BiV* 


Instantaneous 

Photography 


CAPTAIN  ABNEY. 


NEW  YORK : 

THE  SCOVILL  & ADAMS  COMPANY  OF  NEW  YORK, 
60-62  East  Eleventh  Street. 

1896. 


, The 

rPHOTOGRAPHIC 
<MES^ 


^ "An*Illustrated 
f/VONTHLY-AAGAZINE 
DEVOTED-TO-THE* 

, INTERESTS-OF* 

IArtistic&Scientific- 
^ Fhotography 


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A.  C.  LAMOUTTE,  Manairer, 


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THE 


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SC0VILL&  ADAMS  CO.OFN.Y., 

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WALE  & MATHEIN, 

Manufacturers  of 


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We  invite  comparison  with  any  other  make,  at  whatever 
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THE  TURNER-REICH 


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SBNTD  TOR  RARTIOmsAlRS. 

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•Mic  jSB]SD  FQI^  , 


TRIPLEX'lfPROVED 

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Is  Optically  Correct. 

Can  be  used  for  Time  and  Slow  Instantaneous 
Work. 

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Makes  Exposures  from  Time  to  lio  of  a second. 
Is  furnished  with  a Speed  Card. 


The  Teiplex  Impeoted  Shuttee  is  fitted  at  the  diaphragm  of 
lens,  the  only  proper  place  for  a shutter.  Its  speed  is  really  what  is 
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the  ‘‘  speed  indicator”  reads  one  one  . . .th  ” of  a second ! 


The  ‘ATHLETE*  SHUTTER 

I«  u«ed  by  newspaper  staff  photographers,  and  is  unequalled  for 

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’ s Order  of  your  Dealer,  or  from 

X^ROSOXi:  IVEFOr.  CO. 

889,  Broome  Street,  New  York,  N.T. 


INSTANTANEOUS 

PHOTOGRAPHY. 


BY 

CAPTAIN  ABNEY,  c.b.,  r.e.,  d.c.l.,  f.r.s. 


New  York : 

THE  SCOVILL  & ADAMS  COMPANY  OF 
NEW  YORK, 

60-62,  East  Eleventh  Street. 


LONDON 

CARTKR  AND  CO.,  5,  FURNIVAL  STREET,  HOLBORN,  K.C. 


PREFACE. 

— « — > 

The  writer  published  a series  of  articles  on 
instantaneous  photography  in  Photographic 
Work  some  short  time  ago,  and  these  have 
been  re-cast  and  added  to  in  the  present  volume, 
to  form  the  second  of  the  series  of  Photographic 
Primers.  He  trusts  that  in  the  pages  which 
follow,  the  fruits  and  the  results  of  much  experi- 
mental work  will  prove  of  more  than  transient 
value  to  the  readers.  His  desire  has  been  to 
show  that  whether  the  unit  of  time  of  exposure 
be  a second  or  a hundredth  of  a second,  the 
same  rules  have  to  be  followed  to  secure  the 
best  results,  and  that  it  is  worth  considerable 
labour  to  ascertain  what  exposures  are  really 
given  when  an  instantaneous  shutter  is  em- 
ployed. 


South  Kensington,  Aug,  ist,  1895. 


CONTENTS. 

— — ♦ 

CHAP.  PAGE. 

I.  Optical  Apparatus  . . . . . . . . i 

II.  Shutters  . . . . . . . . . . 9 

III.  Speed  of  Shutters  ..  ..  16 

IV.  Quality  of  Shutters  . . ...  . . . . 22 

V.  Shutter  Diagrams  ..  ..  ..  ••  33 

VI.  Lenses  for  Instantaneous  Work  . . . . 49 

VII.  Plates  for  Instantaneous  Work  . . . . 53 

VIII.  Choice  of  Time  for  Instantaneous  Work  ..  58 

IX.  Orthochromatic  Plates  , i ..  ..  63 

X.  Development  of  the  Picture  . . . . . . 67 

XI.  Light  in  the  Dark  Room  ..  ..  ..  71 

XII.  Developing  Formulae  . . . . ..  .-75 

XIIL  Intensification  . . . . . . . . • • 79 

XIV.  Choosing  the  View  . . . . . . . . 86 

XV.  Flash-light  and  Spark  Photography. . 


. 90 


INSTANTANEOUS  PHOTOGRAPHY. 


CHAPTER  I. 

Let  us  just  for  a moment  weigh  the  claims  put  forward 
for  ordinary  photography  to  be  considered  a fine  art,  and 
we  shall  then  be  in  a position  to  see  in  what  respect 
instantaneous  photography  differs  from  it— not  in  any 
carping  spirit,  but  in  the  light  of  the  common  sense 
with  which  we  ol  ttoWoI  are  endowed. 

When  the  reader  speaks  into  a graphophone  or 
phonograph,  the  vibrations  which  his  voice  makes  are 
imprinted  on  a tablet,  and  from  this  tablet  what  has 
been  uttered  can  be  reproduced  mechanically ; but  the 
soft  modulations  of  the  voice  are  absent,  and  there  is 
wanting  a ‘‘  something.’’  So,  in  a photograph,  it  seems 
to  the  writer  that  there  is  the  same  absence  of  modula- 
tion ; the  beauty  which  the  sentient  being,  bestows  is 
wanting,  the  picture  is  mechanically  impressed  on  a 
non-sentient  surface,  which  will  give  a print  with  a deal 
of  the  poetry  of  an  artist’s  drawing  left  out.  What 
the  piano -organ  is  to  the  piano,  so  it  appears  is  the 

B 


2 


INSTANTANEOUS  PHOTOGRAPHY. 


photograph  to  the  artist’s  sketch — there  is  the  want 
of  expression  in  the  former  which  is  present  in  the 
latter. 

This  is  a bad  beginning  for  the  subject  in  hand,  but 
it  really  is  not  inappropriate,  for  taking  this  view  of  the 
subject,  the  practical  making  of  instantaneous  photo- 
graphs cannot  be  the  low  form  of  photography  which 
some  believe  it  to  be.  For  our  own  part  we  believe  its 
results  give  greater  pleasure  to  more  people  than  do  the 
more  carefully  planned  photographs.  It  must  not  be 
considered  for  a moment  that  an  instantaneous  photo- 
graph gives  of  necessity  the  idea  of  motion.  As  a 
matter  of  fact,  it  is  often  grotesque,  and  conveys  the 
idea  that  figures  are  posed  in  attitudes  in  which  they  are 
never  seen,  and  it  is  their  very  grotesqueness  that  often 
makes  them  the  most  interesting,  and  it  might  often 
be  added,  comical.  The  attitude  of  a man  who  is 
caught  whilst  walking,  just  touching  the  ground  with 
the  heel  of  the  preceding  leg,  for  instance,  is  never 
associated  in  the  mind  with  progression  ; nor  do  the 
sharply  defined  spokes  of  its  wheels  give  the  idea  of  the 
rapid  bowling  along  of  a hansom  cab  ; and  yet  both  of 
these  are  seen  in  instantaneous  photographs.  They 
open  out  to  view  what  would  be  seen  if  the  eye  were 
totally  differently  constituted,  and  could  distinguish 
attitudes  taken  up  for,  say,  a i-iooth  of  a second.  As  a 
matter  of  fact,  the  eye  can  scarcely  distinguish  between 
two  attitudes  which  are  separated  by  the  i-ioth  of  a 
second,  if  so  much,  and  those  attitudes  which  make 
the  most  impression  are  those  which  change  least 
rapidly ; and  where  these  are  depicted,  the  idea  is  given 
that  motion  is  taking  place.  Making  allowances  for  the 


INSTANTANEOUS  PHOTOGRAPHY. 


3 


fact  that  instantaneous  photographs  do  not  see  moving 
objects  as  the  eye  sees  them,  they  may  yet  give  scientific 
information,  or  may  amuse,  though  they  may  fail  to 
instruct  in  art. 

It  may  be  well  to  explain  at  the  outset  that  the  epithet 

instantaneous,’’  as  applied  to  photography,  is,  of 
course,  incorrect.  A photograph  taken  by  a flash  of 
lightning  is  not  instantaneous,  for  the  exposure  takes  a 
time  which  is  not  beyond  the  limits  of  measurement. 
The  word,  however,  has  come  to  be  recognised  as 
applying  to  photographs  taken  with  very  short  expo- 
sures ; in  fact,  any  exposure  varying  between  about  the 
I -5th  of  a second  and  the  i -2,000,000th,  which  last  is 
about  the  exposure  which  is  required  to  take  a photograph 
of  a bullet  in  its  flight,  may  come  under  the  head  of  an 
instantaneous  photograph.  It  is  to  such  brief  exposures 
that  we  shall  address  ourselves,  and  endeavour  to  show 
how  the  best  use  is  to  be  made  of  the  appliances  which 
photographers  have  available  for  the  purpose. 

The  first  essential  for  instantaneous  photography  is  a 
lens  that  will  work  with  a fairly  large  aperture  ; if  it  will 
work  with  a stop  inserted,  which  is  i-6th  or  i-8th  of 
the  focal  length,  so  much  the  better  ; but  it  is  available 
if  it  will  only  work — that  is,  give  a fairly  defined  photo- 
graph— with  i-iith  of  the  focal  length.  Some  people 
imagine  that  a lens  which  will  work  without  any  stop 
whatever  is  the  best  to  employ.  But  this  is  a mistake  if 
it  be  a doublet  lens,  for  if  the  track  of  the  rays  be  con- 
sidered, it  will  be  found  that  the  plate  will  inevitably  be 
better  exposed  in  the  centre  than  at  the  margins.  The 
reader  must  remember  that  there  is  often  a fixed  per- 
manent diaphragm  in  the  centre  of  the  lens.  When 


4 


INSTANTANEOUS  PHOTOGRAPHY. 


such  a diaphragm  exists,  it  is  not  a lens  which  can  be 
used  with  full  aperture. 

The  diagram  will  show  why  this  is.  Let  L be  the  lens, 
and  P the  plate,  and  let  us  consider  a point  in  the  margin 
C.  The  only  part  of  the  front  lens  which  will  admit 
light  to  C is  the  small  portion  ah;  the  rest,  a g,  is- 


C 


Fig.  I. 

absolutely  useless.  At  the  centre  of  the  plate  the  whole 
of  the  lens  g h will  be  utilized,  and  consequently  the 
centre  will  be  much  more  exposed  than  the  margin  of 
the  plate.  If,  however,  we  insert  a diaphragm  d d, 
having  an  aperture  e h,  which  just  allows  a c to  pass,  it 
will  be  seen  that  the  central  illumination  is  reduced 
closely  to  the  same  as  the  marginal.  Hence,  in  such  a 
case,  to  secure  equal  illumination,  a diaphragm  is 
absolutely  necessary.  When  choosing  a lens  for  the 
purpose  in  view,  we  must  bear  this  in  mind,  and  it  will 
be  found  that  a lens  whose  components  are  close 
together — that  is,  with  a small  separation  between  them 
— will  be  the  best  lens  to  employ ; for  the  diameter  of 
the  diaphragm  that  may  be  used  will  be  larger  the  less 
separation  they  have.  This  must,  however,  always  be 
coupled  with  the  proviso  that  the  field  is  a flat  field. 


INSTANTANEOUS  PHOTOGRAPHY. 


5 


A flat  field  to  a lens  means  that  the  curvatures  and 
the  refractive  indices  of  the  glasses  used  have  been 
properly  chosen,  and  it  is  only  necessary  to  look  over 
the  long  lists  of  lenses  which  are  made  by  diiferent 
opticians  to  convince  oneself  that  there  must  be  lenses 
which  have  various  states  of  perfection  as  regards  this 
flatness  of  field.  The  photographer,  however,  should 
be  able  to  choose  for  himself,  and  this  is  very  readily 
done  if  he  obtains  possession  of  the  lens  for  trial. 
When  the  writer  obtains  a lens  for  this  purpose,  he 
always  tries  it  at  /jS  and  /ji6.  Now,  a lens  which  can 
take  a picture  which  includes  a wide  angle,  say  65®,  may 
be  taken  as  a rule  as  certain  not  to  cover  the  full  size  of 
plate  with  the  first-named  aperture.  The  margins  will 
be  seen  to  be  wanting  in  definition  if  the  central  part  is 
in  good  focus,  and  vice  versa.  Hence,  for  an  instanta- 
neous picture,  it  is  better  to  include  a more  moderate 
angle  than  that,  say  50^,  when  it  is  probable  that  very 
many  lenses,  which  would  be  unsuitable  for  a plate  of 
the  full  size  they  w^ere  intended  to  cover,  will  give  a 
sharp,  or,  at  all  events,  a very  fairly  sharp  picture  with  a 
smaller  sized  plate.  Thus,  there  are  several  lenses 
extant  which  are  intended  for  a 5 by  4 plate,  which, 
with  an y/8  aperture,  will  not  give  marginal  definition, 
and  yet  will  satisfactorily  cover  a quarter-plate  ; and 
further,  in  which  this  aperture  would  cut  off  part  of  the 
lens  from  work  with  the  larger  plate,  whilst  with  the 
smaller  it  would  be  effective  throughout.  Suppose  a 
lens  of  this  kind  had  to  be  tried,  we  should  proceed  as 
follows.  Put  the  lens  on  a whole-plate,  or  7 J by  5 camera, 
and  mark  in  the  centre  of  a glass  plate  a rectangle  of 
5 by  4,  and  of  4J  by  3J.  Focus  an  image  of  a distant 


6 


INSTANTANEOUS  PHOTOGRAPHY. 


landscape  (with  not  too  much  near  foreground)  on  the 
ground  glass,  and  then  place  the  marked  glass  in  the 
slide,  with  the  back  and  the  front  opened.  The  lens  will 
now  be  exposed  to  view.  Place  in  it  a stop  and  see 
if  from  the  5 -inch  boundary  any  portion  of  the  lenses 
of  the  doublet  is  cut  off  by  the  mount.  It  Is  evident  that 
for  this  size  of  plate  such  a lens  cannot  be  satisfactorily 
used  with  that  diaphragm.  Next,  place  in  the  slot  of 
the  lens  the  next  smallest  diaphragm,  and  again  note 
whether  any  of  the  front  or  back  lens  is  cut  off.  If  it 
should  be,  put  in  the  next  smallest,  and  continue  these 
observations  until  the  stop  is  found  in  which  the  eye 
sees  only  glass  through  the  diaphragm  when  it  is  placed 
against  the  5 -inch  mark  on  the  glass  plate.  Note  what 
diaphragm  just  gives  this  result,  and  remember  that  for 
a satisfactorily  evenly-exposed  picture  no  larger  stop  can 
be  used  with  that  size  of  plate.  Repeat  the  same  obser- 
vations from  the  line  which  marks  the  4J  inch  by  3 f inch 
boundary.  It  will,  of  course,  be  found  that  a larger  stop 
may  be  used  in  this  case  than  when  the  lens  is  viewed 
from  the  5 by  4 inch  line.  If,  as  before  said,  the  lenses 
are  not  widely  separated  and  of  fair  diameter,  a stop  fj% 
should  answer  the  test.  There  are  lenses  which  are  very 
small  in  diameter,  sometimes  the  diameters  of  the  com- 
ponents themselves  being  smaller  than  fj%.  Of  course, 
such  a lens,  though,  perhaps,  useful  for  ordinary  work^ 
should  be  immediately  rejected  for  the  purpose  before  us. 

Supposing  a lens  fulfils  this  first  condition  for  a quarter- 
plate,  the  next  thing  to  do  is  to  take  a negative  of  the 
accurately-focussed  landscape,  with  the //8  stop  inserted^ 


Thus,  if  the  focus  be  6 inches  from  the  diaphragm  to  the  ground  glass,  the 
diameter  of  the  stop  should  be  6-8th  inch  (or  | inch). 


INSTANTANEOUS  PHOTOGRAPHY. 


7 


in  order  to  ascertain  if  the  photographic  focus  is  equally 
as  good,  better,  or  worse  than  the  visual  focus.  It  is 
well  to  take  a large  sized  plate  for  this  purpose,  as  by 
holding  masks  cut  to  the  different  sizes  of  plates  against 
the  negative  it  can  readily  be  ascertained  over  which  size 
the  field  is  sharp.  With  a lens  to  cover  a 5 by  4 plate,  a 
quarter-plate  should  be  almost  perfectly  sharp  if  it  is  to 
be  of  any  use  for  instantaneous  work.  Next  insert  a stop 
y/i6,  and  see  how  much  better  the  focus  is  than  with  //8. 
Everything  ought  to  be  absolutely  sharp  to  the  naked 
eye,  and  if  examined  by  a focussing  glass  it  should  still 
remain  sharp,  and  bear  enlargement,  if  desired.  When 
y*/ 1 6 is  employed,  all  reasonably  near  foreground  should 
also  be  in  focus— in  fact,  everything  beyond  20  feet. 
With  /i^  this  cannot  be  expected  ; we  must  be  content 
if  the  sharpness  is  good  for  everything  beyond  40  feet. 
There  are  some  cheap  lenses  which  never  give  sharp 
images  photographically,  alter  the  focus  as  you  may. 
They  can  be  used  with  a very  small  stop  ; but  for 
instantaneous  work  they  are  perfectly  useless,  unless  by 
those  who  dislike  anything  at  all  sharp  in  a picture.  As 
far  as  the  other  qualities  of  a lens  are  concerned,  we  need 
not  pay  much  attention  to  them.  If  symmetrical,  we 
may  be  tolerably  certain  that  they  will  give  straight  and 
not  curved  lines,  as  the  images  of  straight  lines  at  the 
margin  of  the  plate.  The  colour  of  all  the  glasses  used 
by  opticians  is  very  uniform  throughout,  and  it  may  be 
taken  for  granted  that  no  yery  great  difference  will  be 
found  in  it,  and  that  therefore  one  lens  will  not  be  much 
more  rapid  than  another  from  this  cause.  The  thickness 
of  the  glass  used  has  also  very  little  appreciable  effect, 
unless  it  happens  that  it  be  yellowish,  for  it  will  be  found 


8 


INSTANTANEOUS  PHOTOGRAPHY. 


experimentally  that  a very  thin  layer  of  glass  will 
diminish  the  light  causing  the  photographic  action 
almost  to  the  same  amount  that  a thicker  layer  will  do — 
of  course  within  rational  limits. 

It  may  be  as  well  to  mention  that  the  negative  which 
has  been  supposed  to  be  taken  will  also  show  if  the  lens 
gives  what  is  called  a flare  spot — that  is,  a circle  of 
increased  deposit  at  the  centre  of  the  field.  The  flare 
spot,  it  may  be  observed,  is  due  to  a reflection  of  the 
aperture  of  the  stop,  of  which  it  is  an  enlarged  image. 
Opticians,  however,  now  thoroughly  understand  the 
method  of  making  this  flare  spot  cover  more  than  the 
whole  of  the  plate.  Although  very  appreciable  when 
concentrated  as  a small  patch,  when  the  light  forming 
it  is  extended  over  a large  area  it  becomes  so  attenuated 
in  intensity  that  it  is  practically  absent.  A flare  spot  is 
always  exaggerated  in  effect  when  the  lens  is  dirty ; and 
talking  about  dirty  lenses,  it  must  be  remembered  that  a 
dirty  finger-marked  lens  will  cut  off  and  scatter  as  much  as 
50  per  cent,  of  any  light  which  endeavours  to  pass  through 
it.  This  is  a point  regarding  which  photographers  often 
pay  but  very  little  attention ; but  want  of  cleanliness  often 
has  a serious  effect  when  making  very  rapid  exposures. 
A very  wholesome  piece  of  advice  to  give  to  photo- 
graphers is,  to  clean  the  lens  frequently,  and  not  to  take 
it  for  granted  that  it  is  free  from  dirt. 


CHAPTER  II. 


As  we  have  commenced  by  treating  of  the  optical  part 
of  the  apparatus  necessary  for  instantaneous  photo- 
graphy, we  shall  next  consider  the  method  of  giving  a 
rapid  exposure  by  means  of  what  are  called  instantaneous 
shutters.  Perhaps  on  no  pieces  of  practical  apparatus 
have  more  labour  and  thought  been  expended  than  on 
these.  They  are  often  constructed  on  very  beautiful  and 
ingenious  designs  ; but,  in  many,  something  is  wanting, 
and  they  are  often  far  from  what  we  may  call  ideal 
shutters,  whilst  others  are  as  nearly  perfection  as  may  be. 

The  first  question  is  as  to  the  best  position  that  the 
shutter  should  occupy.  It  is  evident  it  may  be  on  the 
front  of  the  lens,  at  the  back  of  the  lens,  or  occupy  a 
position  close  to  the  diaphragm  ; or,  again,  it  may  be 
placed  close  to  the  plate.  Let  us  see  what  these  several 
positions  entail  in  regard  to  the  general  exposure  of  the 
plate.  We  will  suppose  for  the  moment  that  the  shutter 
is  of  a guillotine  type,  and  that  it  falls  from  the  top  to  the 
bottom,  the  exposure  of  the  lens  beginning  first  at  the 
top,  and  finishing  at  the  bottom.  When  it  is  in  front  of 
the  lens,  as  the  top  part  of  the  lens  is  that  with  which 
the  image  at  the  top  of  the  picture  is  made,  it  is  evident 


10 


INSTANTANEOUS  PHOTOGRAPHY. 


that  the  sky  of  a landscape  is  first  exposed,  then  the 
middle  distance,  and  finally  the  foreground  near  this 
base.  Or  let  us  take  an  example  of  the  figure  of  a man 
moving  across  the  view,  and  whose  image  occupies 
nearly  the  total  height  of  the  plate.  The  hat  will  be 
first  exposed,  then  the  face,  next  the  trunk,  and  finally 
the  legs,  the  last  portion  which  is  impressed  being  the 
feet.  The  photograph  would  not  represent  him  in  the 
position  he  occupied  at  any  particular  instant  of  time, 
but  it  would  represent  the  position  that  his  hat  occupied 
at  one  instant,  his  face  at  another,  and  so  on.  Suppose 
the  guillotine  was  a fairly  narrow  slit,  which  moved 
downwards  at  a moderate  rate,  it  is  evident  that  the 
movement  of  any  small  portion  of  the  image  would  be 
small  during  exposure,  though  the  motions  gone  through 
between  the  time  the  hat  and  the  feet  were  exposed 
might  be  large.  In  fact,  it  might  happen  that  the  image 
on  the  plate  would  show  the  man  as  tumbling  backwards, 
and  the  relative  position  of  the  swinging  arms  to  that  of 
the  legs  actually  reversed,  and  make  the  proportions  of 
the  figure  absolutely  untrue. 

With  the  shutter  at  the  back  of  the  lens  the  attitude 
of  the  man  would  be  reversed.  It  might  show  him  as  in 
the  act  of  falling  forward,  for  the  image  of  his  feet 
would  be  first  exposed,  and  the  hat  last.  Of  course, 
these  are  exaggerated  examples  of  the  want  of  truth 
that  might  be  exhibited,  but  they  are  possible. 

With  the  shutter  close  to  the  plate  the  distortion  is 
much  more  likely  to  be  marked  than  in  either  of  the 
above  cases,  for  even  with  a guillotine  shutter  on  the 
lens  in  which  the  slit  is  moderately  narrow,  the  image 
seen  through  it  at  one  instant  includes  more  than  that 


INSTANTANEOUS  PHOTOGRAPHY.  I I 

width,  for,  were  this  not  so,  the  image  would  not  be  of 
bigger  dimensions  than  the  lens  itself.  With  the  shutter 
close  to  the  plate,  on  the  other  hand,  it  is  the  width  of 
the  slit  which  determines  the  amount  of  image  exposed. 


Fi^.  2. 


The  accompanying  silhouettes  show  what  happens  when 
a narrow  slit  passes  across  the  plate.  A is  the  image  of 
a man  actually  photographed  with  a shutter  at  the 
diaphragm.  At  the  proper  distance  from  the  lens  this 
image  was  made  to  move  at  the  rate  a man  would  move, 
and  exposure  given  to  a plate  with  a guillotine  shutter 
next  the  plate,  the  slit  being  narrow.  B is  the  photo- 
graph obtained  of  A when  the  figure  w^as  moved  in  the 
direction  he  faced  ; and  C when  the  motion  was  in  the 
reverse  direction.  B looks  tumbling  forward,  while  C 
looks  tumbling  backward. 

When  the  shutter  is  placed  near  the  diaphragm  the 
conditions  are  totally  changed.  The  exposures  for  all 
parts  of  the  image  commence  and  finish  together,  and 
are  of  precisely  the  same  duration.  If  it  be  necessary  to 
give  a certain  exposure  to  an  image,  for  satisfactory 
results,  it  is  manifest  that  it  does  not  matter  theoretically 


12  INSTANTANEOUS  PHOTOGRAPHY. 

whether  the  whole  image  is  exposed  for  such  time,  or 
whether  the  different  parts  are  exposed  successively  for 
the  same  time  ; but  it  matters  a good  deal  practically, 
for  the  total  time  occupied  in  giving  the  successive 
exposures  must  necessarily  be  longer  than  that  in  which 
the  exposures  are  given  at  the  same  time ; and  if  the 
camera  be  held  in  the  hand,  the  probability  is  that 
during  the  longer  total  of  successive  exposures  a greater 
movement  in  the  hands  of  the  operator  will  be  found 
than  during  the  shorter  and  simultaneous  exposure. 

The  accompanying  cut  shows  the  movement  of  a hand- 
camera  in  a quarter  of  a second.  The  top  line  is  the 
movement  when  held  in  both  hands  without  any  support ; 
the  second  line  shows  the  movement  when  held  under 
the  chin  and  above  the  chest.  The  third  line  shows 


Fig.  3- 

practically  no  movement.  In  this  case  the  camera  was 
held  in  two  hands,  and  supported  on  an  umbrella  handle. 
The  lowest  line  shows  the  movement  when  held  against 
the  bottom  of  the  chest,  so  that  the  beating  of  the  heart 
and  the  breathing  interfered  with  the  steadiness.  The 
writer  cannot  help  thinking  that  the  diagram  is  very 
instructive,  and  shows  that  practically  perfect  steadiness 
can  be  attained  by  the  use  of  a support. 


INSTANTANEOUS  PHOTOGRAPHY. 


15 


These  records  were  obtained  by  fixing  a vertical  card^ 
in  which  a pinhole  was  pierced,  to  the  camera,  and 
allowing  the  light  from  a stationary  lamp  to  send  a beam 
through  the  hole,  the  image  of  which  was  focussed  on  a 
plate  moving  horizontally. 

On  the  ground,  then,  that  distortion,  and  also  total 
time  of  exposure,  is  minimised  when  the  shutter  is  placed 
at  the  diaphragm,  the  writer  has  come  to  the  conclusion 
that  practically  that  is  the  best  position  for  it.  Another 
point  is  this  : that  the  movement  necessary  in  the  shutter 
itself  is  less  in  this  than  when  in  any  other  position,  as 
the  diameter  of  the  diaphragm  must  ordinarily  be  smaller 
than  that  of  the  surface  of  the  lens  or  plate  itself. 

Let  us  now  consider  as  to  the  circumstances  which 
favour  the  movement  of  a camera  when  held  by  the 
hand,  owing  to  the  release  of  the  shutter.  In  the  first 
place,  it  must  be  borne  in  mind  that  the  camera  and 
shutter  are  practically  one  structure,  and  that  when  the 
shutter  is  placed  ready  for  exposure,  the  combination’” 
has  its  centre  of  gravity  in  some  one  position.  If,  when 
the  shutter  is  moving,  the  centre  of  gravity  shifts  to 
another  position,  a movement,  slight  though  it  may  be^ 
must  take  place  unless  the  camera  be  rigidly  supported. 
There  are  two  ways  of  meeting  this  difficulty  : one  is  to 
make  the  motion  of  the  shutter  symmetrical  on  each 
side  of  the  lens  (in  other  words,  to  close  to  the  centre) ; 
and  the  other  is  to  make  the  movable  parts  of  the  shutter 
as  light  as  possible  compared  with  the  camera.  Now  most 
shutters  are  light,  but  there  are  many  which  do  not  close 
centrally,  and,  in  fact,  as  we  shall  see  shortly,  such  a 
method  of  closing  is  detrimental,  except  when  it  is  placed 
at  the  diaphragm.  Another  point  is,  that  the  release  of 


H 


INSTANTANEOUS  PHOTOGRAPHY. 


the  shutter  should  be  as  light  as  possible,  and  should  not 
be  by  a push  or  pull,  but  by  a pirssure.  All  rifle  shots 
know  that  the  sights  of  a rifle  are  invariably  moved  from 
the  mark  if  the  trigger  is  pulled,  whereas  when  a pressure 
is  applied  between  the  thumb  and  finger  this  does  not 
obtain.  The  release,  then,  should  be  by  a pressure,  and 
all  other  methods  should  be  avoided.  With  the  pneumatic 
arrangement,  of  course,  this  does  not  apply,  for  the 
release  is  then  given  by  an  apparatus  which  is  not  rigidly 
attached  to  the  camera.  For  hand-cameras,  however, 
the  pneumatic  release  is  inconvenient,  though  it  can  be 
effected  by  inflating  the  tube  by  the  mouth  instead  of  by 
pressure  with  the  hand. 

As  regards  the  efficiency  of  a shutter,  the  question  is 
as  to  how  it  is  to  be  judged.  It  is  not  difficult  to  under- 
stand, if  we  have  two  shutters,  both  of  which  give  the 
same  total  duration  of  exposure,  that  if  one  leaves  the 
full  aperture  of  the  lens  uncovered  for  double  the  time 
that  the  other  does,  the  first  one  will  allow  a greater 
quantity  of  light  to  reach  the  plate,  and  will,  therefore, 
be  more  efficient  than  the  second.  In  other  words,  the 
efficiency  of  a shutter  depends  on  the  ratio  of  the  time 
during  which  the  plate,  or  part  of  the  plate,  receives  the 
light  coming  through  the  full  aperture,  to  that  of  open- 
ing and  closing.  Perfect  effciency,  of  course,  would  be 
when  the  time  of  opening  and  closing  is  nil,  and  the 
full  aperture  is  used  throughout.  If  this  theoretic 
efficiency  could  be  secured,  it  is  manifest  that  it  would 
be  immaterial  whether  the  shutter  were  at  the  back,  the 
front,  or  in  the  centre  of  the  lens.  In  comparing  the 
efficiency  of  one  shutter  with  another,  the  standard  that 
is  taken  as  unity  is  the  theoretical  shutter,  but  every 


INSTANTANEOUS  PHOTOGRAPHY. 


15 


part  of  the  plate  has  to  be  considered,  unless  the  shutter 
be  placed  at  the  diaphragm.  What  we  have  to  determine, 
then,  is  the  aperture  uncovered  during  every  small  interval 
of  time,  to  add  these  apertures  together,  and  divide  by 
the  total  duration  of  exposure,  and  compare  it  directly 
with  the  full  aperture.  Thus,  suppose  the  total  duration 
of  the  exposure  was  the  2-0-  second,  that 

At  the  -2-0  0 of  a sec.,  yo  of  the  area  of  the  aperture  was 

[uncovered 

JL 

>>  200  ff  0 

_3._  X 

200  2 >>  >> 

jj  -2  0-0  to  the  2~o  o>  the  whole  aperture  was  uncovered. 
2^0  of  a sec.,  Y of  the  aperture  was  uncovered. 

- A _ JL 

9 f 2 U 0 j > 5 j ) j ) J > 

i 

99  200  j)  1(7  >)  99 

The  efficiency  would  be  (ro+i+i-)  2 + 3,  or  6f  approxi- 
mately, whilst  the  theoretical  perfect  efficiency  would 

6- 

be  10.  The  relative  efficiency  would  be  — , or  *64.  If 

10 

the  areas  uncovered  for  another  shutter  of  the  same 
speed  were  respectively  -^0 , tV,  i,  i,  i , 2 , i,  iV,  Ar,  the 
efficiency  would  be  only  *27. 

If  a plate,  therefore,  with  the  first  shutter  was  just 
enough  exposed,  with  the  second  it  would  be  greatly 
under-exposed. 


CHAPTER  III. 


It  is  much  more  simple  to  ascertain  the  total  speed  of  a 
shutter  than  it  is  the  efficiency,  but  presuming  that  this^ 
first  is  known,  a good  idea  may  be  formed  of  the  latter 
if  the  construction  is  carefully  considered.  No  elaborate 
apparatus  is  required  to  find  the  speed  of  a shutter,  and 
any  amateur  may  carry  out  the  measurement  in  a simple 
manner : first,  without  any  appliance  whatever ; and 
second,  with  an  apparatus  which  can  be  readily  con- 
structed. Let  some  kind  friend  stand  at,  say,  some  20 
feet  away  from  the  operator,  holding  in  his  hand  a roll  of 
white  paper,  and  swing  his  arm  round  in  a circle  in  good 
daylight,  so  that  one  revolution  is  completed  in  one 
second,  and  then  let  an  exposure  with  the  shutter  be  made 
on  this  subject.  The  developed  image  will  show  a move- 
ment of  the  white  roll,  and  if  the  shoulder  be  taken  as  the 
centre  of  the  circle,  the  breadth  of  the  image  of  the  roll 
can  be  measured  at  the  circumference.  Another  photo- 
graph of  the  same  object  when  the  arm  is  still  will  give 
the  true  breadth  of  the  image.  This  breadth  also  can 
be  measured,  and  the  last  measurement  should  be 
deducted  from  the  first,  and  this  will  give  the  amount 
of  movement  which  some  one  point  has  made  during' 


INSTANTANEOUS  PHOTOGRAPHY.  I 7 

the  exposure.  The  circumference  of  the  circle  will  be 
found  by  measuring  the  distance  of  the  shoulder  from 
the  extreme  end  of  the  roll  of  paper,  and  multiplying 
this  by  ^7^.  Having  got  the  circumference,  the  move- 
ment of  the  point  at  the  extremity  of  the  white  roll  is 
divided  into  it,  and  this  will  give  the  fraction  of  a second 
during  which  the  exposure  lasts.  Let  us  take  as  an 
example  : the  width  of  the  image  of  the  roll,  which  when 
still  is  iV  of  an  inch,  and  when  moving  ~ro  of  an  inch. 
The  motion  of  any  point  at  the  extremity  is,  therefore, 
i-Q-  of  an  inch.  The  length  of  the  radius  of  the  circle 
from  the  man’s  shoulder  to  the  end  of  the  roll  is  i-^o 
inches ; the  circumference  is,  therefore,  -ff  by  -7^,  or 
close  upon  8-A-  inches.  There  are  41  times  iV  iu  8tV 
The  speed  of  the  shutter  is,  therefore,  4^-  of  a second. 
By  this  plan  the  rapidity  of  a shutter  can  be  very  readily 
measured  to  within  a small  fraction  of  the  truth,  and 
will  suffice  to  give  an  idea  of  what  objects  can  be  photo- 
graphed by  it  without  movement  being  too  palpably 
visible.  But  we  shall  return  to  this  directly. 

The  next  method  is  more  elaborate,  perhaps,  but  it  is 
very  exact,  and  is  fitted  for  a studio  where  experiments 
can  be  well  carried  on.  It  is  on  the  same  principle.  A 
small  white  sector  is  pasted  on  a black  disc  of  about 
8 inches  diameter,  which  is  attached  to  a spindle,  as 
described  in  the  figure,  and  is  attached  to  a clock-work 
arrangement,  or  can  be  rotated  by  hand. 

The  period  of  rotation  may  be  once  per  second 
exactly ; but  so  long  as  the  period  is  known  it  does  not 
signify  what  the  speed  may  be.  This  period  can  be  very 
accurately  ascertained  by  noting  how  many  revolutions 
are  completed  in  a minute.  In  a case  in  point  it  was 

c 


i8 


INSTANTANEOUS  PHOTOGRAPHY. 


found  that  jii  revolutions  were  made  in  6o  seconds.  The 

6o  83 

time  of  each  revolution  was  therefore  — 7,  or  — of  a 

72J’  100 

second.  The  method  of  procedure  is  exactly  as  before  ; 
but  if  the  camera  has  an  adjustable  focus,  it  is  well  to 
place  it  some  6 feet  off,  and  make  an  exposure  during  a 
revolution.  The  image  made  is  of  the  kind  shown  in 
the  accompanying  figure.  The  angle  through  which  the 


arm  moves  is  measured  by  an  ordinary  protractor;  or, 
better  still,  a white  circle,  with  every  i ® marked  round, 
is  placed  behind  it,  or  in  front  of  it,  and  the  amount  of 
movement  is  read  off ; the  width  of  the  tongue  of  white 
which  revolves  being  also  noted  and  subtracted  from  it. 
In  the  figure  two  exposures  are  shown,  one  in  which  the 
white  sector  is  still,  and  the  other  when  it  is  in  motion. 
It  should  have  been  stated  that,  in  the  first  method,  the 
protractor  can  also  be  used  efficaciously ; but  in  this  case 
the  angle  subtended  by  the  edges  of  the  roll  is  subtracted 
from  the  angle  of  the  edges  when  in  motion,  and  this 
angle  divided  by  360®  gives  the  speed  of  the  shutter. 


INSTANTANEOUS  PHOTOGRAPHY. 


19 


In  the  case  quoted  this  angle  was  found  to  be  9®,  and 
Tf  o is  4^0",  which  is  the  fraction  of  the  second  during 
which  the  exposure  lasts,  which  is  closely  that  arrived  at 
by  the  other  plan  suggested. 

Before  going  further  into  the  method  of  measuring 
rapidities  and  efficiency,  it  may  be  useful  to  ask  what 
rapidity  is  necessary  for  various  moving  objects.  First, 
it  is  necessary  to  remember  that  if  any  point  in  an  object 
is  represented  by  a disc  about  too  of  an  inch  in  diameter, 
it  is  sharp  to  the  eye.  If,  therefore,  all  movement  of  .the 
object  can  in  the  image  be  confined  to  this  amount,  it 
will  appear  sharp.  Now,  with  a hand-camera,  the  focus 
of  the  lens  is  usually  about  5 J inches — let  us  say  6 inches. 
At  50  feet  off,  therefore,  an  object  may  move  through 
I inch  and  still  appear  sharp  — that  is,  the  motion 
during  the  time  of  exposure  may  be  that  amount.  Say 
that  the  time  of  exposure  is  -5-0  second,  it  is  evident  that 
the  object  at  50  feet  off  may  move  at  the  rate  of  50  inches 
— say  4 feet — a second  to  fulfil  the  conditons.  Now,  a 
man  may  walk  two  steps  of  2^  feet  each  in  a second, 
and  supposing  he  moves  uniformly  across  the  view,  he 
would  just  move  a Utile  too  quickly.  Let  him  be  100  ft. 
away,  and  he  would  be  well  within  the  limit  laid  down. 
If  he  were  approaching  or  receding  from  the  camera,  of 
course  the  circumstances  are  changed,  and  the  movement 
he  makes  in  regard  to  the  plate  would  be  a slight  up- 
and-down  motion,  and  no  movement  would  be  perceived 
until  he  was  quite  close  to  the  operator. 

Let  us  take  another  example — an  express  train  going 
about  40  miles  an  hour.  During  one  second  it  moves 
about  60  feet.  If  it  be  desired  to  take  this  at  a distance 
of  1 00  feet  away  whilst  rushing  across  the  field  of  view. 


20 


INSTANTANEOUS  PHOTOGRAPHY. 


it  is  not  hard  to  see  that  a movement  of  6o  feet  would 
require  a rapidity  of  exposure  of  o of  a second.  If  it 
be  taken  at  a distance  of  750  feet  it  would  fulfil  the 
required  condition  with  an  exposure  of  -rj  of  a second. 
Express  trains  have  been  taken,  but  as  a rule  they  are 
coming  in  a marked  degree  towards  the  operator,  which 
immensely  reduces  the  apparent  motion.  The  motion 
of  a breaking  wave  is  small  comparatively,  and  it  will  be 
found  that  for  pictures  of  this  description  iV  second  is 
not  too  small  an  exposure  with  a lens  such  as  is  used 
with  a hand-camera.  It  must  not  be  inferred  that  this 
is  recommended,  but  only  that  such  can  be  given  without 
any  great  loss  of  sharpness.  For  street  views  the  short- 
ness of  exposure  should  only  be  limited  by  the  rapidity 
of  the  plate  and  the  ratio  of  the  aperture  of  the  stop  to 
focal  length  that  can  be  secured.  There  are  scarcely 
any  shutters  which  expose  more  rapidly  than  the  eV  of  a 
second,  though,  of  course,  there  are  some ; but  none 
that  the  writer  has  used  is  less  than  the  to  o'  of  ^ second, 
and  this  is  a very  rapid  rate.  This  remark  only  applies 
to  shutters  placed  at  the  lens  itself,  and  not  to  those 
next  the  plate.  These  last  can  be  made  to  expose  any 
part  of  a plate  for  almost  any  small  fraction  of  a second 
by  narrowing  the  slit  which  passes  across  it. 

When  instantaneous  views  are  taken  with  lenses  of 
longer  focus,  of  course  the  limit  of  motion  in  an  object 
is  narrowed  down  proportionately ; that  is  to  say,  with 
a lens  of  12  inches  focus  the  distances  given  in  the 
examples  must  be  increased  proportionally,  or  doubled. 
This  shows  that  in  the  quarter-plate  picture  it  is  more 
easy  to  secure  sharpness  than  in,  say,  a whole-plate 
picture,  since  the  focal  length  of  the  latter  is,  as  a rule,, 
longer  than  that  of  the  former. 


INSTANTANEOUS  PHOTOGRAPHY. 


21 


We  may  as  well  give  a rule  to  find  what  motion  is  allow- 
able. Divide  the  distance  away  of  the  moving  object, 
in  feet,  by  the  focal  length  of  the  lens  in  feet,  and  divide 
the  product  by  loo,  and  it  will  give  the  result  in  inches. 
Thus  if  an  object  is  90  feet  away  from  the  camera,  and 
the  focal  length  of  the  lens  is  12  inches  (or  i foot), 
the  object  may  move  by  t-oo,  or  i-q-  inches  during 
exposure.  To  ascertain  if  the  shutter  is  sufficiently 
xapid  to  be  within  the  limit,  divide  the  allowable  move- 
ment in  feet  by  the  rate  of  movement  in  feet  per 
second.  Thus,  with  the  above,  if  the  object  were 
moving  i o feet  a second,  the  speed  of  shutter  required 
_ii_x  -i- 

would  be  — — = t"2^  of  a second,  or  about  xio-  of  a 
10 

second,  a time  too  small  for  most  shutters.  If  sharpness 
be  required  with  a shutter  giving  an  exposure  of  -5-0-  of  a 
.second,  the  object  should  be  taken  at  -^(T  X 90  feet, 
,234  feet  off,  or  in  round  numbers  80  yards  off. 


CHAPTER  IV. 


We  have  now  to  explain  how  the  exact  qualities  of  a 
shutter  may  be  ascertained.  The  apparatus  which  is- 
necessary  is  not  in  reality  very  expensive  when  the 
simplest  form  is  used,  but  is  rather  more  complicated 
when  the  more  easily-calculated  diagrams  are  produced. 

The  evolution  of  the  system  employed  may  be  of 
interest.  Let  us  suppose  we  are  dealing  with  a central' 
closing  shutter  outside  the  lens  ; evidently  we  can  throw 
the  image  of  the  diaphragm  of  the  lens  on  a sensitive 
surface,  and  if  that  surface  be  made  to  move — no  matter 
how  for  the  present — whilst  the  shutter  is  making  an 
exposure,  we  shall  get  a blurred  long  image.  If,  how- 
ever, we  fill  the  aperture  with  a card  and  pierce  holes 
round  its  circumference,  instead  of  a blurry  image  we 
shall  get  as  many  lines  of  light  as  there  are  apertures  in 
the  card.  The  length  of  these  lines  will  show  the  time 
during  which  each  of  the  small  holes  was  open. 
Evidently  each  pair  of  holes  which  lie  in  a line  paiallel 
to  the  edges  of  the  moving  pait  of  the  shutter  will  have 
the  same  length  of  exposure,  and  so  would  a hole  in  any 
part  of  the  line  joining  them,  and  consequently  at  the 
point  where  the  central  line  of  the  diaphragm  cuts  it. 
It  follows,  therefore,  that  as  much  information  will  be 
given  if  we  use  only  a slit  running  down  the  centre  of 


INSTANTANEOUS  PHOTOGRAPHY. 


23 


the  diaphragm,  and  instead  of  a series  oflines  we  shall 
have  a plain  figure  formed  by  successive  images  of  such 


The  lines  show  the  diagram  drawn  by  the  holes,  which  were  also  photographed 
with  the  drum  at  rest. 

Fig.  5. 

a slit.  Or  we  may  take  the  shutter  by  itself,  and  place 
in  the  length  of  its  aperture  a card  in  which  a narrow 


C C is  the  card  in  the  aperture  of  the  shutter,  with  a slit  cut  in  it  of  inch 
S S the  shutter  in  the  act  of  closing. 

Fig.  6. 

slit  is  cut  at  right  angles  to  the  direction  of  its  motion ; 
we  can  illuminate  that  slit  by  a condensing  lens,  and  focus 
the  beam  at  the  same  time  on  a photographic  lens,  which 


24 


INSTANTANEOUS  PHOTOGRAPHY. 


will  form  an  image  of  the  slit  on  a surface  placed  at  the 
proper  distance  from  it.  When  the  shutter  is  released, 
the  slit  will  first  be  uncovered,  and  then  gradually 
covered  up  again  (see  fig.  6).  If,  as  before,  the  surface 
on  which  the  image  of  the  slit  is  cast  be  moved,  we  can 
get  a diagram  of  the  slit  showing  what  parts  are  un- 
covered at  every  part  of  the  drop.  If  the  velocity  of 
motion  of  the  receiving  surface  be  known,  we  can  teil 
at  any  instant  of  time  the  amount  of  the  slit  exposed  at 
that  instant.  In  some  experiments  the  motion  given 
to  the  plate  was  circular. 

The  apparatus  was  as  follows  : — A circular  plate,  A, 
on  which  is  placed  a carrier  for  quarter-plate,  or  a 5 -inch 


Fig.  7. 

square  plate,  B,  rotates  in  a dark  slide  by  means  of  a 
spindle  coming  through  the  back  of  A.  To  this  spindle 
an  ordinaay  handle  may  pe  attached,  or  a pulley  which 
may  be  attached  to  it,  and  the  disc  be  rotated  by  any 


INSTANTANEOUS  PHOTOGRAPHY. 


25 


mechanical  means,  such  as  a multiplying  wheel,  or  by 
an  electromotor.  This  dark  slide  can  be  placed  in  an 
ordinary  camera  with  its  plate  ready  for  rotation.  For 
convenience,  a bellows,  C,  for  attachment,  is  useful. 
To  ascertain  what  the  shutter  will  do,  a lens  is  placed 
in  the  camera.  At  a distance  from  the  camera,  and  in 
the  axis  of  the  lens,  is  placed  the  shutter,  with  a fairly 
narrow  slit  placed  close  behind  it  at  right  angles  to  the 
movement  of  the  shutter  wings,  and  centrally.  This  slit 
is  brought  to  a sharp  focus  in  the  plane  of  the  plate, 
and  is  arranged  so  that  the  prolongation  of  the  image 
of  the  slit  would  fall  on  the  centre  of  rotation  of  the 
plate.  Now,  suppose  that  an  exposure  is  given  to  the 
image  of  the  slit  whilst  the  plate  is  rotated  : it  is  evident 
that  we  shall  have  a circular  ring,  the  breadth  of  the 
ring  being  the  length  of  the  slit’s  image.  If,  however, 
the  shutter  is  let  off  whilst  exposure  is  being  given,  we 
shall  have  the  ring  incomplete.  We  shall  first  perceive 
the  bottom  of  the  slit,  then  its  length  gradually  increas- 
ing till  the  shutter  is  at  its  full  aperture,  and  then  see 
the  length  of  the  slit  diminishing.  Such  a negative  will 
give  all  the  information  necessary  as  to  the  efficiency  of 
the  shutter,  supposing  we  know  the  speed  at  which  the 
plate  is  revolving.  The  question  is,  how  to  ascertain 
this.  The  simplest  means  that  the  writer  knows  is  to 
cause  a cardboard  wheel,  with  a convenient  number — 
say  six — of  spokes  in  it,  to  revolve  in  front  of  the  slit 
(see  fig.  8).  When  a bright  light — which  is,  by  the-bye, 
necessary  to  form  an  image  that  can  be  developed — shines 
through  the  slit,  the  spokes  of  the  wheel  cut  it  off  at 
regular  intervals,  which  show  in  the  negative  as  places  of 
no  exposure.  These  intervals  can  be  counted,  and  if  the 


INSTANTANEOUS  PHOTOGRAPHY. 


27 


number  of  times  the  spokes  of  the  wheel  pass  across  the 
slit  be  known,  the  duration  of  the  exposure  is  at  once 
ascertained.  To  ascertain  the  velocity  of  this  wheel,  all 
that  is  only  necessary  is  that  the  rim  be  pierced  with 
holes,  about  3-i6ths  of  an  inch  in  diameter,  at  equal 
intervals  apart.  This  forms  a syren,  and  the  musical 
note  it  gives  when  a current  of  air  is  blown  through  a 
small  glass  tube  against  the  holes  tells  the  velocity  of 
rotation.  The  writer  has  made  his  wheel  to  have  six 
spokes,  and  36  holes  in  the  rim.  It  is  about  8 inches  in 
diameter.  It  rotates  on  an  electro-motor,  and  usually 
gives  a note  about  E.  The  pitch  can  be  compared  with 
the  note  of  a penny  whistle,  which  has,  of  course,  been 
previously  tuned  from  standard  forks.  We  give  a list 
of  the  number  of  vibrations  per  second — that  is,  the 
number  of  times  a hole  of  the  syren  passes  in  front  of 
the  tube  through  which  the  air  is  blown  to  sound  the 
note  commencing  with  middle  C. 


c 

Scientific  scale. 

512 

Society  of  Arts 

528 

C sharp 

540 

559 

D 

..  576  •• 

594 

D sharp 

. . 600 

, . 622 

E 

640 

660 

F 

..  683  .. 

704 

F sharp 

..  720  .. 

..  745 

G 

768 

792 

G sharp 

. . 800 

..  837 

A 

..  853  .. 

..  880 

A sharp 

. . goo 

932 

B 

. . 960 

ggo 

C 

. . 1024 

..  1056 

28 


INSTANTANEOUS  PHOTOGRAPHY. 


There  are,  of  course,  other  temperaments,  the  Dia- 
pason normale”  having  for  C 522,  the  Philharmonic  C 
535,  and  Broadwood’s  is  546.  It  will  be  found  that 
using  either  of  the  two  given  will  not  make  any  serious 
difference  in  the  results,  for  it  must  be  remembered  that 
•each  of  these  numbers  has  to  be  divided  by  6 to  give 
the  number  of  traces  of  the  spokes  per  second. 

If  E be  the  note,  640  holes  pass  through  the  current 
of  air  in  one  second,  or  that  or  107  spokes,  pass 
across  the  slit  per  second.  Supposing  the  shutter  opens 
and  closes  in  the  -gV  second,  6 intervals  of  non-exposure 
will  be  found  in  the  negative  obtained  by  it. 

Thefollowing  is  adiagram  obtained  fromadrop-shutter, 
with  the  motion  accelerated  by  means  of  an  elastic  band. 


Fig.  9. 

It  will  be  noticed  that  there  are  7^  intervals  of  exposure 
shown.  The  wheel  rotated  20  times  in  a second,  as 


INSTANTANEOUS  PHOTOGRAPHY. 


29 


ascertained  by  the  syren,  and  consequently  the  number 
of  non-exposures  per  second  was  120;  the  total  duratior> 

of  the  exposure  was  therefore  or  — second.  The 

72  34 

form  of  the  figure  is  curious;  but  if  the  inner  portion  of 
the  circle  bounding  it  were  spread  out,  so  as  to  be  equal 
to  the  outside  circle,  and  the  figure  straightened,  we 
should  have  an  easily-read  shutter  diagram.  As  it 
is  now,  we  must  take  the  angular  measure  of  the 
figure — that  is,  we  must  see  what  proportion  the  full 
exposure  of  the  slit  bears  to  its  opening  and  closing. 
We  can  then  form  a fairly  correct  idea  of  the  efficiency^ 
of  the  shutter.  In  the  case  before  us,  the  opening 
took  156®,  the  full  aperture  was  uncovered  through 
1 17®,  and  the  closing,  90®.  These  angles  repre- 
sent -tVj  toT?  and  xir-  seconds  respectively  ; that  is, 
the  efficiency  of  the  shutter  was  considerably  less  than- 
the  theoretical  one,  which  would  be  represented  by  the 
total  exposure  of  363®,  multiplied  by  the  length  of 
the  image  of  the  slit.  The  shape  of  the  diagram  shows 
that  the  top  part  of  the  slit  was  exposed  at  a different 
time  to  the  bottom  part.  If,  therefore,  the  shutter  were 
fixed  to  the  front  of  the  lens,  the  top  and  bottom  of  the 
plate  would  receive  the  full  exposure  at  different  times,, 
and  the  liability  to  show  the  distorted  motion  of  an. 
object,  to  which,  in  a previous  chapter,  we  have  called 
attention,  would  be  present.  Again,  it  must  be  remem- 
bered that  the  aperture  of  the  lens  with  which  the  shutter 
would  be  used  is  circular,  and  that  the  time  of  openings 
and  closing  is  therefore  the  opening  and  closing  of  a 
circular  aperture.  As  the  boundaries  of  the  figures,. 
when  opened  out  as  described,  are  nearly  straight  lineSy 


30 


INSTANTANEOUS  PHOTOGRAPHY. 


and  as  the  full  aperture  is  a circle,  the  efficiency  when 
the  full  aperture  is  uncovered  is  measured  by  its  area 
into  the  time  during  which  it  was  open.  The  efficiency 
during  the  opening  and  closing  will  be  represented  by 
the  length  of  the  exposure  occupied  in  so  doing  multi- 
plied by  half  the  area,  as  this  last  gives  the  mean  aperture. 
The  rule  to  apply  to  ascertain  the  total  efficiency  of  a 
shutter  is  to  add  to  the  time  of  full  exposure  half  the 
times  of  closing  and  opening,  and  to  divide  the  result 
by  the  total  time  of  exposure.  We  have  here  a ready 
means  of  finding  out  this  most  important  quality  of 
a shutter.  In  the  case  in  point  the  efficiency  is 

lie  + (A-  + tir)  i ^ diaphragm  be 

3ir 

inserted  in  the  lens,  all  we  have  got  to  do  is  to  put  the 
shutter,  during  the  experiment,  on  the  lens,  and  focus 
the  slit,  as  before,  on  to  the  plate,  and  repeat  the 
operations  just  described,  with  the  slit,  however,  across 
the  diaphragm.  We  shall  then  get  a diagram  of  the 
movement  of  the  shutter,  and  can  calculate  the  efficiency 
in  the  same  way.  It  will  be  found  that  the  smaller  the 
diaphragm,  the  more  efficient  is  the  shutter ; and  it  can 
be  readily  seen  that,  when  the  diaphragm  is  a pin’s 
point,  the  actual  very  nearly  approaches  theoretically 
perfect  efficiency. 

It  may  be  interesting  to  show  the  appearance  of  the 
diagram  when  pinholes  are  pierced  in  a card  filling  the 
aperture,  the  piercing  being  round  the  diaphrcgm.  In 
the  case  in  point,  six  pinholes  were  pierced  at  equal 
intervals  round  it,  and  a central  one  was  also  added. 
The  conditions  of  the  exposure  were  precisely  the  same 
as  when  the  slit  was  used,  though  the  plate  revolved 


IxNSTANTANEOUS  PHOTOGRAPHY. 


31 


.a  little  slower.  The  intervals  in  the  broken  lines  show 


Fig.  10. 


Key  shutter  diagram. 

Fig.  II. 

the  times  when  the  exposuies  were  stopped  by  the 


32 


INSTANTANEOUS  PHOTOGRAPHY. 


rotating  wheel  placed  in  the  beam.  The  middle  line  is- 
that  given  by  the  exposure  through  the  central  pinhole. 
The  readers  may  trace  out  for  themselves  which  is  the 


Drop  shutter  diagram. 
Fig,  12. 


top  and  which  the  bottom  pinhole.  It  will  be  seen  at 
once  that  the  figure  is  much  less  easy  to  deal  with  than 
when  one  central  slit  is  used.  Figs,  ii  and  12  show 
diagrams  taken  in  the  manner  before  described.  The 
velocity  of  rotation  was,  however,  arrived  at  by  a method 
which  will  be  subsequently  explained. 


CHAPTER  V. 

The  most  convenient  method  of  getting  a shutter 
diagram,  however,  is  by  means  of  a rotating  drum.  The 
figure  illustrating  the  drum  is  inserted  here  in  order  that 
a comparison  may  be  made  between  the  two  methods 
-employed.  In  this  case  the  procedure  is  exactly  the 
same  as  before,  only  the  shutter  is  placed  so  that  the 


Fig.  13. 


line  of  motion  is  horizontal,  and  the  slit  is  placed,  as 
before,  parallel  to  that  line,  so  that  the  image  falls 
horizontally  on  the  middle  of  the  drum. 


D 


34 


INSTANTANEOUS  PHOTOGRAPHY. 


A celloidin  film,  or  a sheet  of  bromide  paper,  can  be 
wrapped  round  it,  and  secured  by  a collar  fitting  tight 
at  one  edge,  and  by  an  elastic  band  at  the  other.  The 
diameter  of  the  drum  was  exactly  41V  inches,  and  allow- 
ing for  the  thickness  of  the  film,  its  circumference  when 
charged  with  the  sensitive  surface  amounted  to  almost 
exactly  1 3 inches,  and  this  length  of  circumference  was- 
taken  as  sufficiently  accurate  when  the  revolutions  were 
counted  or  known  by  the  note  given  out  by  the  syren. 
If  the  drum  revolved  twice  a second,  evidently  the  surface 
moved  through  26  inches  : if  three  times,  39  inches,  and 
so  on.  In  a large  majority  of  cases  it  made  100  revolu- 
tions in  27  seconds,  or  3*7  revolutions  in  one  second  ;; 
that  is,  it  travelled  48  inches  in  one  second,  so  that  in 
Toir  second  *48  inch  passed  a given  spot.  Evidently 
with  this  speed  of  rotation  any  moderately  short  exposure 
could  be  measured.  When  the  exposure  was  too  long 
for  this  speed,  a fly-wheel  of  cardboard  was  attached  to 
the  spindle  of  the  drum,  and,  according  to  its  weight,  so- 
was  the  speed  reduced. 

The  image  will  be  the  same  as  if  received  on  a flat 
surface  moving  uniformly  up  and  down,  the  drum  being 
only  an  artifice  to  secure  this.  It  has  already  been 


Fig.  14. 

said  that  if  the  figure  taken  on  the  rotating  plate  be 
straightened  out,  we  shall  get  a diagram  which  can  be 
easily  measured.  The  accompanying  figure  is  a diagram 


INSTANTANEOUS  PHOTOGRAPHY. 


35 


given  in  the  last  chapter  so  straightened,  being  taken  on 
the  drum.  It  will  be  seen  that  the  shutter  was  set 
slower,  loj  intervals  being  seen  instead  of  y^-,  for  the 
‘‘  wheel”  was  rotating  at  the  same  speed  as  before.  The 
efficiency  calculated  by  adding  the  time  of  exposure 
during  which  the  whole  aperture  was  open  to  half  the 
time  during  which  it  was  opening  and  closing,  and 
dividing  the  same  by  the  total  time  of  exposure, 
is  *66. 

In  some  cases  where  the  jaws  of  the  shutter  are  not 
straight — as,  for  instance,  in  a Furnell  shutter — it  is 
useful  to  take  diagrams  with  the  slit  at  right  angles 
to  the  direction  of  motion,  as  well  as  parallel  to  it. 
This  enables  a graphic  method  of  estimating  the 
efficiency  to  be  adopted,  instead  of  what  becomes  a 
rather  laborious  calculation.  Fig.  15  shows  the  diagram 


of  this  shutter  taken  as  above.  By  simple  measurement, 
the  aperture  of  the  shutter  at  any  instant  can  be 
known,  the  one  figure  being  a check  upon  the  other. 
Fig.  1 6 shows  the  apertures  at  empirically  fixed  intervals. 
The  syren  also  tells  us  that  the  number  of  revolutions 
of  the  drum  was  22  per  second.  The  time  interval 
between  two  ribs  being  known,  and  being  a certain 


36  INSTANTANEOUS  PHOTOGRAPHY. 

distance  apart,  and  the  circumference  of  the  drum 
being  also  known,  it  is  easy  to  calculate  the  speed  of 
rotation. 

One  other  very  simple  plan  of  getting  the  number  of 
revolutions  of  a wheel  is  to  attach  it  to  a counting 
machine.  We  have  used  for  this  purpose  an  old  turnstile 
counter.  It  registers  units,  tens,  hundreds,  thousands, 
and  ten  thousands.  By  noting  how  many  numbers  are 
registered  in  a minute,  the  speed  per  second  can  be 
readily  found. 

A time-scale  can  also  be  impressed  on  the  plate  with 
Ihe  diagram,  by  means  of  a tuning  fork,  to  which  a 


Aperture  at  different  periods  of  the  exposure. 
Fig.  16. 


light  card  having  a narrow  vertical  slit  cut  in  it  was 
attached,  the  slit  on  the  drum  being  horizontal.  By  a 
lens  an  image  of  this  vertical  slit  was  made  to  fall 
exactly  in  focus  on  the  horizontal  slit,  and  after  a diagram 
had  been  taken  the  fork  and  lens  were  placed  in  position, 
the  shutter  closed,  and  another  exposure  made.  The 
small  square  bright  area  made  by  the  intersection  of  the 
two  slits  gave  a sinuous  line  on  the  moving  surface  due 
to  the  fork’s  vibrations.  The  number  of  vibrations  per 
second  being  known,  that  line  became  a scale. 

Fig.  17  will  give  an  idea  of  the  arrangements  adopted. 


INSTANTANEOUS  PHOTOGRAPHY. 


37 


Lg  is  a 1 2-inch  R.R.  lens  screwed  into  the  door  of  a 
dark  room,  within  which  the  drum  and  the  motor  were 
placed  at  a proper  distance  for  the  focus.  (In  the  later 
arrangement  the  use  of  a dark-room  for  exposure  became 
unnecessary,  the  drum  being  attached  to  a camera.)  Out- 
side E is  the  electric  arc  light,  and  Li  is  a lens  throwing 
an  image  of  the  white-hot  positive  pole  on  a circular 
aperture  in  the  one  end  of  a collimator  (which  is  simply  a 
tube  with  a lens  at  one  end,  and  the  aperture  at  the  other 


Apparatus  for  making  a parallel  beam  pass  through  the  shutter  and  the 
camera  lens.  It  also  shows  the  tuning  fork  in  position. 

Fig.  17. 

placed  exactly  at  its  equivalent  focus).  The  rays  issue  out 
of  C as  parallel  rays,  and  if  1'  and  L2  are  out  of  the  way, 
fall  on  the  lens  of  the  camera  B through  the  shutter,  and 
practically  form  an  image  of  a distant  point.  The  rays 
pass  on  to  L3,  where  they  are  collected,  and  form  an  image 
of  the  aperture  of  the  diaphragm  in  the  camera  lens.  Im 
these  experiments  the  diaphragm  was  filled  with  a thin. 
card,  in  which  a slit  was  cut  traversing  its  horizontal 
diameter.  Thus  a horizontal  line  of  light  was  thrown 
on  the  drum.  The  drum  being  set  in  motion,  a couple 
of  exposures  with  the  shutter  were  made,  and  it  then 


38  INSTANTANEOUS  PHOTOGRAPHY. 

became  necessary  to  put  the  time  scale  on.  T is  a 
tuning  fork,  attached  to  which  is  the  card,  in  which  a 
vertical  slit  is  cut.  The  card  S is  placed  in  the  path  of 
the  beam  as  shown,  and  a sharp  image  of  the  vertical 
slit  thrown  on  the  card  fitting  the  diaphragm.  Thus  a 
single  very  small  square  of  light  reaches  the  drum,  and 


Thornton  and  Pickard  special  shutter  diagram,  with  tuning  fork  vibrations 
shown.  (Taken  with  slit  at  diaphragm  of  the  lens.) 

Fig.  18. 

an  image  formed  of  the  intersection  of  the  two  slits. 
The  tuning  fork  is  set  vibrating  by  a bow,  and  two 
more  exposures  are  made,  and  the  vibrations  cause  a 
sinuous  line  to  be  impressed,  each  sinuosity  being  due 
to  a complete  vibration  of  the  fork.  On  development, 
the  diagram  the  shutter  made  by  its  motion  across  the  slit, 
together  with  the  record  of  the  vibrations,  are  brought 
out.  An  arrangement  whereby  the  two  were  impressed 
together  was  found  to  be  inconvenient  and  unnecessary. 


INSTANTANEOUS  PHOTOGRAPHY. 


39 


as  the  period  of  rotation  of  the  drum  remained  the  same 
during  many  experiments  when  the  apparatus  remained 
unaltered.  It  may  be  remarked  the  further  away  from 
L3  that  the  fork  was  placed,  the  more  marked,  as  might 
be  expected,  were  the  sinuosities.  When  using  the 
camera  lens  and  its  diaphragm,  the  arrangement  to 
secure  parallel  rays  became  essential,  for  evidently  if  the 
beam  converged  through  the  shutter,  the  eclipsing  of 
the  diaphragm  would  commence  sooner  than  it  would 
with  parallel  rays.  It  became  easy  by  this  arrangement 
to  test  the  shutter’s  efficiency  for  any  part  of  the  plate 
that  was  desired.  All  that  was  necessary  was  to  twist 
the  camera  B horizontally  to  such  a position  that  the 
image  of  the  hole  at  the  end  of  the  collimator  fell  on  its 
focussing  screen  at  the  desired  part,  and  then  to  proceed 
as  before. 

The  following  is  a diagram  obtained  by  this  apparatus, 
and  it  will  be  seen  how  very  suggestive  it  is : — 


Drop-shutter  diagram. 

Fig.  19. 

It  may  be  asked  why  the  shutter  without  the  lens  was 


40 


INSTANTANEOUS  PHOTOGRAPHY. 


used.  For  instance,  in  hand-cameras,  would  it  not  have 
been  better  to  use  its  own  lens  with  its  stop,  as  that  is 
how  it  is  practically  used  ? Of  course,  in  such  a case 
the  slit  should  be  at  the  diaphragm,  for  that  is  the  place 
where  it  would  naturally  be  of  most  use.  All  that  the 
slit  at  the  diaphragm  would  give  would  be  a diagram  of 
the  rapidity  of  exposure  at  the  centre  of  the  plate,  or  at 
any  one  desired  part  by  twisting  the  axis  of  the  camera 
lens  into  the  desired  direction,  whilst  what  was  required 
was  the  rapidity  and  efficiency  at  any  point  of  the  plate. 
The  sole  exception,  of  course,  is  a shutter  opening  at 
the  diaphragm,  where  the  whole  plate  is  equally  exposed. 

Diagrams  of  several  shutters  which  may  be  of  interest 
are  shown.  Thornton  and  Pickard’s  special  shutter^ 


Thornton  and  Pickard’s  shutter.  Diagrams  taken  with  slit  in  the  aperture- 
of  the  shutter. 

Fig.  ^o. 

which  is  a shutter  placed  outside  of  the  lens,  and 


INSTANTANEOUS  PHOTOGRAPHY.  4^ 

has  wings  opening  and  closing  centrally,  is  a good 
specimen.  We  have  two  diagrams  on  each  strip.  One 
was  made  with  the  spring  wound  to  give  the  quickest 
exposure,  and  the  shutter  itself  wound  to  its  full  extent 
(Fig.  20).  That  gives  a very  short  diagram,  only  some 
-A-  of  a second.  The  second  diagram  is  the  same, 
only  the  shutter  was  wound  so  as  only  to  just  close 
the  aperture.  In  another  diagram  the  spring  of  the 
shutter  was  not  wound  so  tight,  but  the  shutter  itself 
was  wound  as  before.  The  difference  between  the  first 
two  will  be  seen.  All  four  have  practically  the  same 
shape,  and  the  times  of  opening  and  closing  to  and 
fromx  full  aperture  have  closely  the  same  proportion  to 


Hawkins’  shutter  diagram,  taken  with  slit  in  the  aperture  of  the  shutter. 
Fig.  21. 


the  full  aperture  exposure  in  all  cases.  The  centre  of 
the  plate  gets  more  exposure  than  the  margins,  as  can 
be  seen  by  treating  the  diagram  as  that  of  the  Hawkins 
shutter  will  be  immediately. 

How  the  shutter  diagrams  can  be  utilized  is  shown  in 
the  annexed  figure,  which  needs,  perhaps,  a little  ex- 
planation. S S S S is  the  diagram  of  one  of  Hawkins^ 


42  instantaneous  phoiOgraphy. 

shutters,  which  is  a shutter  with  an  aperture  crossing  the 
back  of  the  lens.  Supposing  we  have  a line  which  is 
drawn  in  section  to  the  same  scale,  we  can,  by  placing  it 
sectionally  at  the  distance  from  the  shutter  at  which  it 
is  proposed  to  use  it,  tell  what  exposure  will  be  given 
to  any  part  of  the  plate,  and  how  much  later  or  earlier 
one  part  will  be  exposed  than  another.  The  scale  of 
speed  in  t-oo  second  is  attached.  The  beams,  as 
refracted,  are  not  shown  in  the  diagram,  but  some 
beams  will  issue  through  the  stop  and  come  out,  as  aa, 


To  show  what  part  of  the  shutter  diagram,  taken  with  slic  at  the  aperture  of 
the  shutter,  is  utilized  by  rays  passing  at  difer^nt  angles  through  the 
diaphragm. 

Fig.  22. 

bb,  cc.  Where  these  cut  the  shutter  they  are  pro'ected 
by  parallel  lines  on  to  the  shutt.m  diagram,  and  the 
deeper  shaded  parts,  ABC,  show  which  part  of  the 
shutter  will  be  utilized  by  such  rays,  d'he  amount  of 
full  aperture  is  shown  beneath.  It  will  be  seen  in  this 
shutter  diagram,  as  indeed  in  all,  that  the  parts  used  are 


INSTANTANEOUS  PHOTOGRAPHY. 


43 


practically  bounded  by  sloping  straight  lines.  These 
show  the  moment  when  the  shutter  begins  to  open  and 
arrive  at  full  aperture,  or  when  it  starts  from  full  aper- 
ture and  closes.  Calculation  shows  that,  with  a uniform 
motion  of  a plane  across  a circle,  the  exposure  is  half 
that  which  would  be  given  were  the  aperture  fully  open 


To  illustrate  the  different  efficiencies  of  a shutter  when  it  is  fixed  at  different 
distances  from  the  diaphragm. 

Fig.  23. 

for  the  same  time.  (This  we  have  used  in  a former 
chapter,  and  the  reason  for  it  will  now  be  seen.)  Now  the 
practically  straight  boundary  lines  show  that  the  motion 
of  opening  and  shutting  may  be  considered  as  uniform. 
Under  these  circumstances  it  is  easy  to  calculate  the  actual 
exposure,  and  compare  it  with  the  theoretically  perfect 
exposure  : we  only  have  to  take  the  mean  of  the  bases  of 
the  little  triangles,  and' ’-add  it  to  the  length  of  the 


44 


INSTANTANEOUS  PHOTOGRAPHY. 


exposure  of  full  aperture.  This  has  to  be  compared  with 
the  total  length  of  exposure.  Thus  for  the  centre  rays  the 
bases  of  the  side  triangles  are,  roughly,  9 and  7,  and  of 
the  full  aperture  exposure,  24.  The  exposure  in  terms 
of  full  aperture  is  thus  8 + 24=  32;  the  theoretical 
exposure  is  9 + 7 + 24  = 40  ; the  practical  exposure  is 
thus  *75,  or  f that  of  the  theoretical.  In  this  way  the 
exposure  at  any  part  of  a plate  can  be  worked  out,  and 
if  the  illumination  of  the  field  with  full  aperture  is  known 
by  other  measures,  the  uniformity  or  otherwise  of  ex- 
posure can  be  ascertained.  All  shutters  which  move 
across  a lens  can  be  treated  in  the  same  way.  We  can 
here  show  the  dilference  that  the  distance  of  the  shutter 
from  the  lens  makes  in  its  general  efficiency.  The  diagram 
of  the  Thornton  and  Pickard  special  shutter  (fig.  23) 
will  well  illustrate  this.  It  will  be  seen  that  if  the 
shutter  is  in  the  position  Q,  it  is  much  more  efficient  for 
the  marginal  rays  than  it  is  when  in  the  position  P.  It 
may  be  stated  as  an  axiom  that  the  nearer  the  shutter 
is  to  the  diaphragm,  the  more  equally  efficient  it 
becomes  for  the  entire  plate  ; and  the  further  away  the 
less  efficient,  taking,  of  course,  the  efficiency  for  the 
central  rays  as  the  standard  of  comparison. 

We  may  here  point  out  that  a comparison  of  the 
results  obtained,  by  getting  the  time  scale  from  the 
syren,  and  those  obtained  with  the  tuning  fork,  show 
that  either  plan  is  effective.  In  the  one  case  the  time 
of  exposure  for  the  central  rays  was  found  to  be  -9^-  of  a 
second,  and  with  the  other  -9V,  fifteen  “ turns  ’’  being 
given  to  the  ratchet  of  the  spring  in  both  cases. 

The  case  of  a shutter  like  that  of  the  Key  camera, 
which  is  a shutter  at  the  diaphragm  opening  with  a 


INSTANTANEOUS  PHOTOGRAPHY, 


45 


square  aperture,  has  to  be  differently  calculated.  In  it 
^ve  have  a space  gradually  opening  from  and  closing  to 
the  centre.  The  diagram  of  this  shutter  is  instructive. 
If  the  lens  were  square  instead  of  circular,  the  exposure 
for  any  diaphragm  would  be  given  by  the  cubic  content 
.of  a square  prism,  and  of  square  pyramids  terminating 


Key  shutter  diagrams. 

No.  I,  taken  through  a diaphragm //8. 

No.  2,  ,,  ,,  „ //i6. 

Fig.  24. 

it.  In  Other  words,  you  have  to  take  the  length  of  full 
aperture  exposure,  and  add  to  it  ^ the  length  of  time 
. elapsing  between  full  aperture  and  opening  and  closing. 
There  is,  however,  a slight  correction  to  be  made  for 
the  circular  segments  (for  the  diagram  was  made  with 
the  slit  parallel  to  one  pair  of  sides  of  the  square 


46 


INSTANTANEOUS  PHOTOGRAPHY. 


aperture,  and  placed  centrally).  When  these  are  made, 
the  efficiency,  with  a stop  y/8,  is  expressed  by  *51,  and 
with  y7i6  stop;  *72.  This  shows  also  that  you  do  not  gain 
fou7^  times  the  exposure  by  using  y/8  stop  when  compared 
with  /ji6  stopf  hut  only  about  three  times,  which  is  a 
thing  to  be  remembered.  In  the  same  diagram  is 
shown  the  theoretical  exposure  with  /1 16  stop,  cut  out 
of  the  y/8  diagram,  and  alongside  is  the  actual  diagram 
made  with  the  latter  stop.  The  two,  it  will  be  seen,  are 
identical. 

The  shutter  placed  at  the  diaphragm  which  should 
give  a nearer  approach  to  a factor  of  efficiency,  unity,  is 


Key  shutter  diagrams,  one  taken  with  nearly  full  speed,  and  the  second  with 
some  “ break  ” on. 

Fig:  25. 

one  made  somewhat  after  the  Key  fashion,  but  instead 
of  closing  as  a square,  should  close  with  parallel  sides. 
If  the  Key  shutter  were  on  this  principle,  and  had  the 
same  velocities,  the  speed  efficiencies  for  y/8  and  fjih 
stops  would  be  *64  and  *79.  (This  kind  of  shutter  we 
have  in  one  of  Adams’  hand-cameras.  A still  nearer 
approach  would  be  when  only  one  plane  crossed  the 
aperture.)  Fig.  25  is  a double  shutter  diagram,  one 
being  taken  with  nearly  full  speed  of  shutter,  and  the 


INSTANTANEOUS  PHOTOGRAPHY. 


47 


other  with  some  break  on.  It  will  be  seen  from  it  that 
the  relation  between  time  of  exposure  with  full  aperture 
and  total  exposure  remains  constant. 

Where  an  aperture,  of  no  matter  what  shape,  crosses 
the  lens  by  a radial  motion,  the  calculations  are  not 
quite  so  simple  ; and  in  such  a case  it  may  be  advisable 
to  revert  to  the  plan  of  piercing  holes  in  a card  round 
the  aperture,  and  make  each  hole  draw  its  own  lines^ 
and  from  such  a diagram  to  make  the  calculations. 
There  are  several  lessons  to  be  learnt  from  these 
diagrams.  In  the  first  place,  no  shutter  has  perfect 
efficiency,  and  not  one,  with  the  exception  of  the- 
diaphragm  shutter,  exposes  the  whole  of  the  plate  at  the 
same  time.  The  shutter  which  works  across  the  back 
or  the  front  of  the  lens,  in  which  there  are  two  wings- 
opening  at  one  side  and  closing  at  the  other,  can  be 
made  to  give  fairly  equal  exposures  over  every  part  of 
the  plate,  though  the  start  often  has  the  best  of  it. 
The  shutter  which  works  in  front  of  the  lens,  closing 
and  opening  centrally,  gives  the  margins  less  exposure 
than  the  centre ; but  the  exposure  may  be  made  fairly 
equable  when  the  lens  is  shallow— that  is,  when  the 
shutter  is  fairly  close  to  the  diaphragm.  The  further 
off  it  is,  the  more  the  difference  in  exposure  shows.. 
The  shutter  which  works  across  the  lens  with  only  one 
wing,  as  in  the  drop  shutter,  exposes  one  margin  more 
than  the  centre,  and  the  centre  than  the  other  margin. 
Hence  it  may  be  usefully  employed  in  landscape  work, 
where  the  sky  can  receive  slightly  less  exposure.  The 
bigger  the  lens,  of  course  the  less  rapid  the  shutter,. 
With  the  diaphragm  shutter  the  smaller  the  stop  the 
more  nearly  is  unity  of  efficiency  obtained,  and  the 


48 


INSTANTANEOUS  PHOTOGRAPHY. 


larger  the  stop  the  less  efficient  it  is.  A greater 
efficiency  is  obtained  by  a shutter  which  moves  across 
the  diaphragm  than  with  one  which  opens  and  closes 
centrally.  The  light  that  may  be  used  for  these  diagrams 
was  the  electric  light,  but  very  satisfactory  results  have 
been  obtained  by  using  a strip  of  magnesium  ribbon,  or 
hy  a continuous  vertical  stream  of  magnesium  powder 
blown  through  a spirit  flame,  after  the  fashion  of  Nadar’s 
lamp. 

In  reference  to  these  devices  for  getting  a shutter 
•diagram,  it  may  be  stated  that  there  is  nothing  very 
difficult  in  making  a flat  plate  cross  the  path  of  the  ray  of 
light  coming  through  the  slit,  provided  it  be  sufficiently 
long.  Equality  of  motion  is  not  necessary,  for  it  is  the 
intervals  of  non-exposure  in  the  plate  which  tell  us  the 
time  of  exposure.  Nothing  else  is  required.  On  a 
whole-plate,  for  instance,  with  a little  adroitness,  it  is 
comparatively  easy  to  get  a shutter  diagram  by  simply 
•dropping  it  across  the  image.  Again,  too,  it  is  not 
necessary  to  have  any  mechanical  means  of  making  the 
plate  or  the  drum  rotate.  A good  spin  given  by  the 
hand  suffices  to  give  them  sufficient  motion  for  the 
purpose,  and,  as  before,  the  number  of  intervals  of  non- 
exposure  in  the  developed  image  suffices  to  indicate  the 
time  of  exposure.  This  simplifies  the  apparatus  con- 
siderably. 

We  may  sum  up  by  saying  that  the  form  of  shutter 
which  gives  no  distortion  is  that  placed  at  the  diaphragm, 
.and  that  the  worst  is  that  placed  close  to  the  plate  ; that 
no  shutter  has  perfect  efficiency,  but  is  nearest  to  possess- 
ing it  when  a small  diaphragm  is  employed. 


CHAPTER  VI. 


The  question  of  a lens  for  instantaneous  work  has 
already  been  touched  upon,  but  we  must  revert  to  it 
again  in  connection  with  the  instantaneous . shutter 
which  has  to  be  used.  From  the  shutter  diagrams  which 
have  been  made,  examples  of  which  have  been  shown  in 
the  previous  chapter,  it  is  manifest  that  the  larger  the 
aperture,  the  less  approach  to  theoretical  efficiency  a 
shutter  will  possess.  This  is  because  the  time  during 
which  the  full  aperture  of  the  stop  is  uncovered  is  much 
longer  with  a small  aperture  than  with  a large  one, 
always  supposing  that  no  change  in  the  extent  of  the 
movement  of  the  shutter  is  made  when  a stop  is  changed. 
The  total  tivie  of  exposure  will  always  be  the  same,  what- 
ever stop  be  used  ; and  if  an  object  is  moving  at  a rate 
which  shows  no  perceptible  blurring  of  the  image  due 
to  that  motion  when  the  shutter  is  set  at  a certain 
speed,  whatever  stop  is  employed  the  same  want  of 
sharpness  of  image  due  to  that  cause  will  always 
obtain.  If,  however,  we  slow  ” down  the  shutter,  we 
have  at  once  a tendency  for  the  blurring  of  the  object 
to  be  increased.  It  thus  is  apparent  that  it  is  better  to 
use  a larger  stop  to  obtain  proper  exposure  than  it  is  to 


50  INSTANTANEOUS  PHOTOGRAPHY. 

slow  down  the  shutter,  provided,  of  course,  the  lens 
covers  properly  when  the  larger  aperture  is  employed. 
If  a lens  has  been  critically  tried,  as  explained  in  a 
previous  chapter,  we  can  tell  what  is  the  limit  to  which 
we  may  enlarge  the  aperture  without  losing  definition 
due  to  the  imperfections  of  the  lens,  and  we  can  safely 
increase  the  total  exposure  bv  using  a stop  up  to  that 
aperture,  but  not  further.  When  more  exposure  is 
required  than  this  will  give,  we  must  put  the  break  on 
the  shutter  and  slowdown  its  speed.  With  some  lenses 
which  are  made  with  Jena  glass,  we  can  use  an  aperture 
of  about  /j6 — that  is,  i of  the  focal  length — without 
any  loss  worth  mentioning  in  the  definition  of  the  field  ; 
and  with  such  a lens  it  may  safely  be  said  that,  as  a 
rule,  the  shutter  should  not  be  slowed,  for,  if  it  has  to 
be,  it  is  pretty  certain  the  conditions  are  such  that 
instantaneous  phonography  is  difficult. 

The  point  now  presents  itself  as  to  what  speed  the 
shutter  should  be  confined.  There  are  very  few  shutters 
extant  which  give  an  exposure  of  the  to^  of  a second  ; 
the  -fiV  of  a second  is  much  more  common.  As  a-  rule, 
for  distant  views  with  figures  not  too  close,  the  -gV  of  a 
second  is  the  shortest  exposure  that  is  absolutely 
necessary,  whilst  many  objects  need  not  have  less  than 
iV  of  a second,  such  objects  being  breaking  waves,  and 
ordinary  landscapes,  even  with  trees  blowing  about,  and 
so  on.  For  rapidly  moving  objects,  if  the  to^  of  a second 
can  be  secured,  so  much  the  better,  and  a large  stop  must 
be  used  with  a good  light.  This  shows  that  there  is  a 
variation  allowable,  even  with  the  shutter,  and  in  certain 
conditions  of  weather  it  is  a distinct  advantage  to  have 
the  use  of  the  slower  shutter,  and  also  the  larger  stop ; 


INSTANTANEOUS  PHOTOGRAPHY.  5 I 

but  we  would  much  prefer  to  use  a quick  speed  of 
shutter  with  a large  stop,  than  a less  rapid  speed  with 
a smaller  stop.  For  instantaneous  work  the  iris  dia- 
phragm to  a lens  is  an  admirable  adjunct,  for  it  is 
distinctly  an  encouragement  for  the  photographer  to 
alter  the  stop  instead  of  the  rapidity  of  the  shutter. 
The  insertion  of  a Waterhouse  diaphragm  takes  time, 
and  of  all  things  perhaps  in  instantaneous  photography 
time  is  the  most  precious,  and  this  the  photographer 
often  gains  by  using  the  break  to  the  shutter,  rather 
than  by  altering  the  stop.  The  iris  diaphragm  is  an 
old  invention,  but  if  the  writer  had  to  name  a re-invention 
which  deserves  special  praise,  it  is  that  of  this  handy 
kind  of  diaphragm.  To  sum  up,  regarding  lens,  dia- 
phragm, and  shutter,  we  may  say  that  a lens  which  can 
work  with  a flat  fleld  and  sharp  with  a stop  //6,  which 
has  an  iris  diaphragm,  and  a shutter  which  closes 
in  the  sVth  of  a second,  are  what  we  should  look 
for  in  instantaneous  work.  A single  lens  is  some- 
times recommended,  but  its  drawback  is  the  distortion 
of  straight  lines.  Though  not  quite  useless  for 
architectural  work,  or  for  views  in  which  buildings  are 
to  be  found,  yet  it  is  unsatisfactory,  and  can  rarely  be 
used  with  a stop  so  large  as  that  with  which  a doublet 
can  be  used.  It  gives  a brighter  image  because  it  has 
fewer  reflecting  surfaces ; but  the  brightness  rarely 
exceeds  by  more  than  ten  per  cent,  that  of  a good 
colourless  doublet  lens;  for,  as  stated,  the  thickness  of 
glass  through  which  light  passes  has  but  little  to  do 
with  the  falling  off  of  the  intensity.  The  first  thin 
layer,  which  must  be  alike  in  both  single  and  doublet 
lens,  is  that  which  has  most  effect.  A striking  example 


52  INSTANTANEOUS  PHOTOGRAPHY. 

of  this  was  given  by  Professor  Boys,  who  showed  that 
the  difference  in  chemical  action  on  a plate  when 
shielded  by  microscopic  glass,  or  by  glass  of  ordinary 
thickness,  was  practically  the  same  in  both  cases.  It 
will  be  judged  that  the  shutter  which  we  most  prefer 
is  between  the  lenses,  and  this  naturally  confines  our 
choice  to  some  few  which  are  specially  adapted  for  it. 
We  may  mention  the  shutter  supplied  by  the  Platinotype 
Company  with  their  Key  camera,  and  the  latest  Furnel 
shutter,  as  good  types  of  diaphragm  shutters;  whilst  for 
those  working  outside  the  lens  we  have  many.  Amongst 
the  very  best,  as  giving  a gQod  diagram,  we  may  men- 
tion the  Thornton-Pickard  shutter.  It  may  be  taken 
as  a maxim  that  the  less  complicated  the  shutter  is, 
the  more  satisfactory  it  will  be  in  the  long  run.  The 
fewer  things  there  are  to  get  out  of  order  the  better, 
and  a simple  shutter  is  always  more  easy  to  repair,  and 
is  less  expensive  to  renew.  For  instantaneous  work 
that  is  carried  out  in  a camera  fastened  to  a camera- 
stand  the  drop-shutter  is  very  satisfactory  when  it  is 
light,  but  care  must  be  taken  that  it  does  not  shake  the 
camera  in  the  act  of  letting  off.  This  liability  to  shake 
is  much  less  with  shutters  to  which  a pneumatic 
arrangement  is  attached,  for  reasons  which  will  be 
obvious.  With  a hand-camera  a shutter  of  this 
description  is  almost  inadmissible,  for  it  is  apt  to  come 
in  contact  with  the  hands  when  the  catch  is  released. 
The  pneumatic  principle  of  release  here  requires  a third 
hand,  or  a substitute  for  such  a hand,  and  therefore  the 
method  of  releasing  by  hand  must  be  resorted  to, 
though  in  some  cases  the  mouth  may  be  used  to  inflate 
the  teat  which  effects  the  release. 


CHAPTER  VII. 


A QUESTION  is  very  often  asked  as  to  what  plates  should 
be  used  in  instantaneous  photography.  There  are 
certain  essential  characteristics  which  may  be  mentioned 
without  giving  any  brand  a gratuitous  advertisement. 
A plate  for  instantaneous  work  should  not  be  starved 
in  emulsion,  but  it  should  be  fairly  dense  when  looking 
through  it.  Such  being  the  case,  one  may  expect  that 
of  necessity  the  plates  will  not  always  be  the  cheapest 
in  the  market,  for  if  they  were  sold  at  the  lowest  price, 
the  amount  of  material  that  is  employed  would  run  the 
profits  very  fine.  If  it  be  thinly  coated  there  is  not 
much  latitude  in  exposure,  and  for  this  kind  of  work  it 
is  essential  that  there  should  be  ; for  although  a plate 
has  some  one  exposure  which,  with  a certain  mode  of 
development,  is  probably  the  best,  yet  deviation  from 
this  exposure  has  to  be  allowed  for,  and  this  is  secured 
by  having  a good  thickness  of  film.  It  should  also  be 
as  rapid  as  possible,  and  the  method  of  arriving  at  a 
conclusion  regarding  the  rapidity  will  be  touched  on 
presently. 

The  plate  should  also  be  evenly  coated,  which  implies 
that,  amongst  other  things,  the  glass  should  be  as  flat  as 


54 


INSTANTANEOUS  PHOTOGRAPHY. 


can  be  obtained.  The  glass  used  for  ordinary  plates  is 
anything  but  uniformly  flat,  and  if  the  best  work  is  to 
be  carried  out  with  ordinary  photography,  this  flatness 
should  be  secured.  It  need  scarcely  be  said  that  the 
plate  should  be  free  from  spots  which  refuse  to  develop, 
or  from  spots  which  develop  too  much  ; in  other  words, 
it  should  be  as  perfect  as  possible,  and  as  rapid  as 
possible.  It  may  further  be  remarked — and  this  applies 
to  all  kinds  of  photography — that  the  methods  very 
often  adopted  for  separating  plates  from  each  other  are, 
in  many  cases,  inadequate.  There  is  nothing  more 
annoying  than  to  find,  on  an  otherwise  perfect  negative, 
marks  due  to  the  rubbing  together  of  the  sensitive 
surfaces  of  two  plates.  If  the  plates  were  really  flat, 
this  could  not  occur,  since  the  strips  of  that  paper 
forming  the  separation  would  be  sufficient  to  prevent 
it.  One  maker,  at  least,  has  adopted  the  plan  of 
cutting  through  the  glass  of  a double-sized  plate 
without  breaking  the  gelatine  film,  and  folding  the  two 
face  to  face.  This  is  an  excellent  plan,  since  the  films 
are  immovable,  and  even  when  the  glass  is  not  quite 
flat,  no  rubbing  marks  are  found.  Another  disadvantage 
of  separating  plates  by  edgings  of  thick  paper  is,  that 
they  may  often  show  markings  where  the  paper  has 
been  in  contact  with  these.  Sometimes  these  parts  are 
fogged,  and  sometimes  seem  as  if  sensitiveness  had 
been  lost.  Some  makers  pack  with  thin  paper  between 
the  surfaces,  and  when  such  paper  is  free  from  con- 
tamination it  answers  well ; but  in  this  case  the  maker 
is  very  much  in  the  hands  of  the  paper-maker.  If 
plates  or  films  are  not  intended  to  be  kept  long,  this 
plan  will  answer,  however,  when  care  in  the  selection 


INSTAJSTTANEOUS  PHOTOGRAPHY. 


55 


of  the  paper  has  been  exercised.  As  a rule,  if  one  plate 
in  a box  shows  spots,  the  others  will  also  have  this 
defect.  A very  crucial  test  is  to  expose  a plate  to  naked 
candle  light  for  a period  sufficiently  long  to  cause  the 
surface  to  blacken  under  development.  Any  trace  of 
opaque  or  insensitive  spots  will  be  at  once  seen,  and 
if  they  are  numerous,  or  of  a pronounced  character, 
beware  of  the  remainder ! One  defect  that  is  now 
rarely  met  wdth  is  incorrectness  in  cutting  the  plates 
to  the  proper  size.  There  is  nothing  much  more 
annoying  than  this,  and  it  is  a defect  for  which  the 
plate-maker  is  absolutely  responsible. 

Now  as  to  the  rapidity  of  a plate.  It  is  not  intended 
to  enter  into  the  methods  which  a plate-maker  may 
adopt  for  the  purpose  of  measuring  it ; more  especially 
as  there  is  more  than  a suspicion  that  the  comparative 
rapidities  of  a plate  may  alter  according  to  the  intensity 
of  the  light  employed.  The  following  plan  will,  however, 
give  a very  good  idea  of  how  the  rapidity  of  a plate  can  be 
guaged.  Take  a quarter-plate,  say  of  medium  rapidity, 
but  giving  good  density,  and  expose  a strip  of  it  to  an 
ordinary  paraffin  candle,  at  a distance  of  six  feet,  for 
five  seconds,  an  adjoining  strip  for  ten,  another  for 
twenty,  and  so  on,  each  time  doubling  till  an  exposure 
of  640  seconds  has  been  arrived  at  (a  strip  of  the  plate 
should  remain  unexposed).  Now  develop,  and  we  have 
a scale  of  different  transparencies.  In  a case  in  point, 
the  following  were  the  transparencies  of  the  different 
strips,  calling  o sec.,  100;  5 sec.,  83*5;  10  sec.,  65; 
20  sec.,  40;  40  sec.,  24;  80  sec.,  10*5;  160  sec.,  5; 
320  sec.,  2*7  ; 640  sec.,  1*5.  If  we  place  this  scale  of 
transparency  in  contact  with  the  plate  to  be  tried  in  the 


5 6 INSTANTANEOUS  PHOTOGRAPHY. 

dark  slide  in  the  camera,  using  the  lens  with  an  aperture 
of  y/8,  or  whatever  aperture  it  is  proposed  to  employ, 
and,  with  the  shutter  set  at  its  usual  rapidity,  give  an 
exposure  on  a bright  day  to  the  reflection  of  the  sun 
from  white  paper,  or  to  an  evenly-lighted  sky,  an  image 
of  the  scale  of  shade  will  be  produced.  If  the  plate  is 
sufficiently  rapid  to  be  impressed  by  the  light  coming 
through  the  densest  strip,  such  as  given  above,  it  may 
be  taken  that  the  plate  is  fit  for  the  purpose  of  instanta- 
neous photography.  Two  or  three  plates  may  be  tried 
at  the  same  'time,  by  cutting  them  into  strips,  and 
giving  an  exposure  together. 

On  a cloudy  day,  or  when  there  is  a blue  sky,  the 
test  will  be  still  more  exacting ; but  if  a plate  which  is 
known  to  be  fit  for  the  work  be  exposed  with  that 
under  trial,  a very  good  notion  of  the  compara- 
tive rapidities  can  be  obtained.  It  is  better,  as  said 
before,  to  use  daylight  if  possible,  than  any  artificial 
light  in  these  trials.  It  must  further  be  recollected  that 
the  visual  brightness  of  the  image  seen  on  the  focussing 
screen  by  no  means  represents  the  true  photographic 
brightness.  The  ground  glass  itself  allows  a great  deal 
of  the  light  to  pass  through  it,  and  only  a percentage 
forms  the  image  on  the  screen.  If  the  true  brightness 
has  to  be  seen,  it  should  be  viewed  on  an  opaque  white 
screen,  from  which  all  light  except  that  of  the  image 
itself  is  excluded,  when  at  once  the  difference  will  be 
manifested.  Further,  it  must  be  recollected  that  the 
photographic  is  very  different  to  the  visual  value  of  day- 
light. Sunlight  is  said  to  have  a visual  illuminating 
power  of  5,000  candles  if  they  could  all  be  placed  at 
one  foot’s  distance  from  a white  screen.  If  this  be  so, 


INSTANTANEOUS  PHOTOGRAPHY. 


57 


it  has  a photographic  value  of  100,000  candles  at  the 
same  distance.  So,  in  order  to  estimate  visually  the 
photographic  value  of  the  camera  image  with  a stop  /IS 
in  comparison  with  one  formed  by  candle-light,  it  would 
be  necessary  to  insert  a stop  about  y/i‘8  to  give  it ; or, 
again,  the  brightness  of  an  image  with  /jS  will  be 
visually  about  the  photographic  brightness  of  an  image 
when  using // 36, 


CHAPTER  VIIL 


The  question  next  arises  as  to  when  an  instantaneous 
photograph  can  be  taken.  This  point  has,  in  some 
measure,  already  been  referred  to  before.  The  writer 
believes  that,  under  moderate  conditions  as  to  weather, 
there  is  no  day  at  any  time  of  year,  with  a rapid  plate, 
on  which  an  instantaneous  photograph  of  a fairly  open 
landscape  may  not  be  taken  between  the  hours  of  nine 
in  the  morning  and  three  in  the  afternoon  by  using  a 
stop  of /j8,  with  a shutter  which  can  give  the  one-tenth 
of  a second’s  exposure.  On  a bright  day  in  summer  the 
stop  that  can  be  used  is  often  as  small  as  y/22,  and 
even  /1 32,  with  an  exposure  of  one-fiftieth  of  a second. 
This  means,  on  the  old  system  of  calculation,  supposing 
y/2  2 be  used  in  summer,  that,  with  equally  well-exposed 
negatives,  the  light  (say  in  December)  is  forty  times 
less  photographically  intense  than  in  July,  or,  if  y/i6  is 
used,  ten  times  less  intense.  This  is  not  far  from  the 
truth.  As  an  example,  it  may  be  stated  that,  with  one 
of  the  most  rapid  plates  in  the  market,  early  in 
December,  about  ^ 1 1 a.m.  on  a cloudy  day,  with 
occasional  gleams  of  sunshine,  perfectly  exposed  nega- 
tives of  near  oak-trees,  with  old  brown  foliage  on  them. 


INSTANTANEOUS  PHOTOGRAPHY. 


59 


in  Richmond  Park,  were  obtained  under  the  circum- 
stances described.  The  same  trees  were  taken  in  the 
previous  July  with  /jit,  about  lo  a.m.,  the  shutter  set  to 
give  one-fiftieth  second,  and  the  exposure  was  more  than 
sufficient,  although  the  shadows  were  very  heavy.  As  a 
rule,  the  amateur  puts  away  his  photographic  kit  for 
instantaneous  work  as  soon  as  the  short  days  commence. 
This  is  a mistake,  for  effects  can  often  be  obtained  at 
such  a time,  owing  to  the  low  altitude  of  the  sun,  which 
cannot  be  found  on  days  which  are  long.  Abroad,  par- 
ticularly at  high  altitudes,  where  the  air  is  clearer  and 
the  sun  brighter,  views  can  be  obtained  later  in  the  day 
(or  earlier)  than  at  home  ; for  instance,  with  fjS  and 
one-twentieth  of  a second  exposure,  good  views  in  fairly 
wide  streets  of  Rome  have  been  obtained  in  January 
up  to  3*45  p.m.  The  writer  has  obtained  in  the 
middle  of  February  views  in  the  city  (London)  which 
have  been  fully  exposed.  It  cannot,  however,  be  too 
much  insisted  upon  that,  for  such  purposes,  really  rapid 
plates  should  be  employed.  It  must  not,  however,  be 
considered  that  any  view  can  be  taken  under  these 
circumstances.  For  instance,  a path  through  a wood 
or  a narrow  street  is  impracticable  very  often  under 
apparently  favourable  conditions.  Let  us  consider  the 
case  of  the  narrow  street  view.  It  is  highly  improbable 
that  much  sun  can  reach  it  even  in  summer,  and  much 
less  so  in  the  winter.  The  illumination  is,  therefore, 
that  due  to  the  sky.  Now,  though  the  light  from  the 
whole  sky — or,  say,  from  half  the  sky — may  be  sufficient 
to  illuminate  a wall  so  as  to  impress  the  photographic 
plate,  yet  if  we  have  but  a small  fraction  of  the  sky- 
light available,  as  is  the  case  in  such  a street  view,  it  is 


6o 


INSTANTANEOUS  PHOTOGRAPHY. 


manifest  that  the  illumination  must  be  deficient,  and  no 
amount  of  ''coaxing’’  in  development  will  give  a satis- 
factory picture. 

The  writer  has  seen  amateurs,  and  some  who  ought 
to  know  better,  go  into  a gallery  wainscoated  with  fairly 
dark  oak,  and  give  an  instantaneous  exposure  to  obtain 
a negative.  Seemingly  to  such,  if  an  apparatus  is 
labelled  as  suitable  for  instantaneous  work,  any  and 
every  view  is  to  be  taken  with  a shutter.  One  trait  in 
the  general  character  of  a young  photographer  is  his 
credulity.  He  has  implicit  faith  in  the  use  and  meaning 
of  words,  but  forgets  that  photographic  goods — like  the 
pedlar’s  razors — are  often  made  to  sell. 

In  calculating  the  stop  to  use  and  the  exposure  to 
give,  the  photographer  should  pay  attention  to  several 
things  before  making  his  final  determination.  He 
should  see  how  much  sky,  for  instance,  is  available  for 
illuminating  the  darkest  part  of  his  picture  ; also 
whether  the  local  colour  is  a good  one  for  reflecting 
photographic  light.  Thus,  a red  brick  wall  is  not  so 
good  as  a grey  stone  wall,  for  obvious  reasons  ; or  the 
dark  green  foliage  of,  say,  a fir-tree,  not  so  fit  for 
reflecting  the  necessary  light  as  the  paler  green  of  an 
elm,  and  so  on.  He  should  determine  to  expose,  as  far 
as  possible  or  practicable,  for  the  deep  shadows,  so  as  to 
get  something  in  them  beyond  general  transparency. 
It  may  be  noted  here  that,  in  any  close  views,  there  is 
scarcely  any  probability  of  over-exposing  when  a shutter 
is  employed,  the  dark  shadows  being  usually  very  black 
through  want  of  atmosphere  between  the  lens  and  the 
object.  For  open  views  this  is,  however,  by  no  means 
the  case.  There  is  always  a certain  amount  of  " sky  ” 


INSTANTANEOUS  PHOTOGRAPHY. 


6r 


present  between  the  lens  and  the  object,  and  in  the 
photograph  this  sky  is  impressed.  The  word  sky  is  used 
here  advisedly.  The  blue  light  in  the  sky  is  caused  by 
small  floating  particles  in  the  atmosphere  which  scatter 
more  of  the  blue  than  of  the  yellow  and  red  rays  of  the 
spectrum — that  is,  these  last  are  more  transmitted, 
whilst  the  first  go  to  form  the  blue  of  the  sky.  These 
particles  are  particularly  present  near  the  surface  of  the 
ground,  and  they  scatter  and  reflect  the  light  similarly 
to  those  particles  which  are  above  us. 

Over-exposure  on  a thinly-coated  plate  means  a flat 
image,  which  only  intensification  subsequently  can  render 
possible  for  printing  purposes.  It  should  also  be  remem- 
bered that  white  objects  in  the  foreground  (say,  a white 
road)  are  difficult  to  deal  with,  but  they  are  useful  for 
reflecting  light  into  the  deeper  shadows.  When  the  sun 
is  high  in  a cloudless  sky  it  is  well-nigh  impossible  to 
get  a good  landscape  view  ; the  shadows  are  too  short 
and  too  black  to  deal  with  successfully  under  any  circum- 
stances, and  especially  for  instantaneous  work.  It  is 
impossible  to  fix  any  altitude  for  the  sun  with  which  not 
to  work,  for  so  much  depends  upon  the  character  of  the 
sky.  If  there  be  fleecy  clouds  about,  which  act  as 
reflectors  of  a good  deal  of  the  sunlight,  views  may  be 
taken  which  should  not  be  attempted  if  the  sky  were 
clear.  On  a bright  summer’s  day  it  is  not  a bad  plan  to 
take  a siesta  before  noon,  have  lunch,  and  afterwards 
smoke  a quiet  pipe,  and  then  begin  serious  work.  By 
this  time  the  sun  will  have  sunk  to  a reasonable  altitude, 
and  the  hard  work  of  the  day  will  commence.  On  a 
grey  day  the  camera  may  be  at  work  without  any  such 
pleasant  interval,  and  the  effects  will  be  almost  as. 


62 


INSTANTANEOUS  PHOTOGRAPHY. 


pleasing — or  as  little  pleasing — at  one  time  as  at 
another. 

When  the  sun  is  only  about  twenty-five  degrees  above 
the  horizon,  exposures  will  have  to  be  prolonged.  The 
stop  should  be  changed  to  a larger  one  then,  and,  as 
sunset  approaches,  one  still  larger  should  be  inserted ; 
and  as  a last  resort,  the  shutter  should  be  slowed,’’  as 
already  explained.  Not  many  photographers  at  hom^e 
are  accustomed  to  see  sunrises  in  summer,  but  those 
who  do  should  follow  the  same  rules  as  for  sunset  work. 
It  is  often  said  that  the  light  is  better  at  sunrise  than  at 
sunset.  This  is  so  in  some  cases,  but  as  often  the 
reverse.  If  the  sun  rises  or  sets  very  red,  the  light  will 
be  worse  than  if  it  sets  orange  or  yellow. 


CHAPTER  IX. 


The  writer  has  recently  been  using  orthochromatic  plates 
with  a screen  for  instantaneous  views,  and  has  come 
to  the  conclusion  that  under  certain  conditions,  and  for 
some  purposes,  they  are  at  an  advantage  over  the 
ordinary  sensitive  plate.  In  the  market  there  are 
several  brands  of  orthochromatic  plates — isochromatic, 
they  are  sometimes  called — all  of  which  have  a certain 
amount  of  sensitiveness  to  certain  colours  by  which  the 
ordinary  plate  is  almost  unaffected.  These  orthochro- 
matic plates  may  be  classed  into  two  kinds,  some  which 
are  sensitive  to  the  yellow  and  green  rays  (besides  the 
blue  and  the  violet),  and  the  others  which  are  sensitive 
to  red  and  yellow  (besides  the  blue  and  the  violet).  If 
we  examine  a landscape  through  an  orange  glass  we 
shall  find  that  the  blue  sky  appears  darker  than  it  is  in 
reality,  whilst  the  faintest  white  clouds,  which  we  hardly 
distinguish  when  viewed  without  the  glass,  become 
well-marked  objects.  The  green  of  foliage  and  grass  is 
also  ren  dered  yellower,  whilst  a red  brick  house  appears 
unchanged.  These  effects  are  produced  by  reason  of 
the  orange  glass  cutting  off  the  violet  and  a large  amount 
of  the  blue  rays  which  exist  in  the  light.  Evidently,  in 


64  INSTANTANEOUS  PHOTOGRAPHY. 

order  to  benefit  by  this  absorption  of  those  rays  which 
are  principally  active  in  ordinary  photography,  we  must 
have  a plate  which  is  sensitive  to  the  colours  transmitted. 
Both  kinds  of  orthochromatic  plates  will  answer  this 
purpose,  though,  of  course,  they  will  require  longer 
exposure  when  such  a screen  is  employed  in  conjunction 
with  the  lens.  With  the  orange  glass  employed  the 
writer  found  that  an  exposnre  twelve  times  more  pro- 
longed was  required  than  that  for  the  same  plate  when 
no  screen  was  employed. 

The  plates  employed  were  sensitive  to  yellow  and 
green,  as  well  as  to  the  blue.  Using  a stop  of  y/i6  it 
was  found  that  an  ordinary  exposure,  without  the  yellow 
glass,  was  about  the  -A-th  of  a second  in  March  on  a 
fairly  open  view.  The  lens  employed  was  such  that 
most  perfect  definition  could  be  obtained  when  y/5‘6 
was  employed  over  the  whole  of  a quarter-plate.  Now 
this  stop  means  that  about  eight  times  more  light  is 
admitted  to  a plate.  If  the  shutter  used  had  the 
same  efficiency  with  /js’^  that  it  had  with  y/i6,  it  is 
evident  that  the  speed  might  have  been  reduced  to 
“A-th  of  a second  to  get  proper  exposure  with  the  yellow 
glass  inserted.  As  a matter  of  fact,  it  is  not  quite  so 
efficient,  so  the  shutter  was  slowed  down  till  it  gave  an 
exposure  of  Arth  of  a second.  When  this  was  done  an 
exposure  through  the  orange  glass  with  an  aperture  //S'b 
was  found  ample.  In  summer  weather  the  speed  may 
be  diminished  to  the  -Ath  of  a second,  and  satisfactory 
pictures  can  be  got. 

The  explanation  of  the  altered  appearance  of  the  sky 
when  viewed  through  the  orange  glass  may  be  given 
here. 


INSTANTANEOUS  PHOTOGRAPHY. 


65 


In  sky-light  there  are  proportionally  many  more 
blue  and  violet  rays  for  an  equal  intensity  of  light  than 
there  are  in  sunlight.  Now  clouds  are  simply  reflectors 
of  sunlight  when  they  are  seen  as  white.  It  can  there- 
fore be  very  readily  seen  that  as  the  orange  glass  cuts  off 
nearly  all  blue  and  violet  rays  from  every  kind  of  light, 
it  will  leave  the  sky  apparently  much  darker  than  it  does 
the  clouds,  and  as  the  residual  light  affects  the  plate,  it 
will  be  affected  in  closely  the  same  proportion  as  the 
brightness  which  the  two  seem  to  be  to  the  eye.  If  no 
screei^be  used,  the  larger  proportion  of  blue  light  in  the 
sky  will  make  it  relatively  more  photographically  actinic 
than  the  clouds,  and  hence  there  may  be  little  or  no 
distinction  between  the  two. 

Discretion  must  be  used  in  choosing  the  glass. 
There  are  various  tints  of  orange,  and  even  a light 
yellow  glass  is  often  effective,  particularly  when  the  sun 
gets  low.  A light  yellow  glass  will  only  prolong  the 
exposure  three  or  four  times,  and  is  very  suitable  for 
afternoon  views.  In  choosing  the  glass,  care  must  be 
taken  that  it  is  optically  flat.  If  the  image  of  a window 
be  viewed  on  the  surfaces  of  the  glass,  and  the  window 
bars  remain  undistorted  when  the  glass  is  turned  in 
every  direction,  it  may  be  assumed  that  the  glass  is 
sufficiently  flat  for  the  purpose. 

Another  plan  is  to  place  a piece  of  white  card  at  a 
distance  of,  say,  five  feet  from  the  glass,  and  reflect  a 
beam  of  sunlight  (not  transmitted  through  a window 
pane)  on  to  it.  If  the  glass  is  flat,  the  patch  of  sunlight 
on  the  card  should  be  of  about  the  same  size  as  the  glass 
itself,  and  show  no  striae  or  markings.  It  may  happen 
that  a part  will  appear  to  be  without  any  flaws,  judging 

F 


66 


INSTANTANEOUS  PHOTOGRAPHY. 


by  the  patch  of  light  on  the  card,  and  this  part  may  be 
used,  if  sufficiently  large,  to  cover  the  lens.  Worked 
glass  can  be  obtained,  but  it  is  expensive,  and  usually 
some  small  area  in  the  ordinary  coloured  glass  may  be 
found  which  will  be  sufficiently  plane  as  judged  by 
either  of  the  above  methods. 

When  a piece  is  chosen,  it  should  be  placed  in  situ 
(the  writer  prefers  it  behind  rather  than  in  front  of  the 
lens),  and  the  image  of  a distant  landscape  be  examined. 
A newspaper  may  be  substituted  for  the  landscape  if 
more  convenient.  The  image  should  be  as  sharp  with 
the  glass  as  without  it. 

With  the  lens  the  writer  used,  the  screen  could  not 
be  placed  at  the  diaphragm,  as  there  was  no  room  for 
it ; but  with  some  lenses,  for  the  usual  metal  stop  one  of 
cardboard  may  be  cut  out,  and  picked  thin  microscopic 
glass  be  coated  with  collodion  in  which  aurantia  has 
been  dissolved,  and  placed  in  the  aperture  so  cut.  There 
seems  to  be  a future  for  instantaneous  orthochromatic 
photography  on  the  lines  indicated  above. 


CHAPTER  X. 


Development  of  the  picture  is  the  next  point  we  have 
to  consider,  and  this  is  by  no  means  unimportant.  One 
thing  has  to  be  recollected,  and  this  is,  that  a very 
rapid  plate  is  very  frequently,  hut  not  always^  difficult  to 
develop  with  bare  shadows.  We  may  first  of  all  con- 
sider what  we  really  have  to  develop  compared  with  an 
ordinary  artificial  light.  Measuring  the  camera  image 
with  a stopy/8  by  means  of  an  amyl-acetate  lamp,  it  will 
be  found  that  the  sky  has  a value  varying  from  five  of 
these  units  on  a grey  day,  to  three  times  that  value  on  a 
really  bright  day,  and  that  the  highest  light,  such  as 
brilliantly  illuminated  clouds,  is  again  three  or  four  times 
brighter ; whilst  the  deepest  shadow  that  is  required  to  be 
shown  has  a value  of  about  73V  of  the  same  unit.  Roughly 
speaking,  it  may  be  said,  then,  that  the  highest  light  on 
bright  days  is  about  250  times  brighter  than  that  of  the 
deepest  shadow. 

This  has  to  be  rendered  on  a print  with  a comparative 
brightness  of  about  30  to  i,this  being  somewhere  about 
that  of  white  paper  to  platinum  black  as  found  in  a 
platinum  print.  It  is  quite  evident,  then,  that  if  it  were 


68 


INSTANTANEOUS  PHOTOGRAPHY. 


possible  in  the  negative — which  it  is  not — to  have  a 
difference  between  the  transparency  of  the  deposit  given 
by  the  highest  light  used,  and  the  deepest  shadows  of 
250  and  I,  and  all  the  intervening  gradations  in  proper 
relation,  that  by  far  the  largest  part  of  the  print  would 
either  show  black  with  gradations  in  the  whites,  or  whites 
with  gradation  in  the  shadows.  What  we  have  to  do  is 
to  reduce  the  gradation  of  the  negative  as  far  as  possible 
proportionally.  This  means  that  the  image  must  be 
full  of  detail  throughout,  and  at  the  same  time  have  the 
highest  light  shown  as  white,  and  the  deepest  shadows 
as  black.  This  is  a problem  which  requires  careful 
attention,  and  depends  on  two  factors:  ist,  the  plate 
used  ; 2nd,  the  method  of  development,  and  kind  of 
developer.  Now  the  quicker  the  plate  in  a bright  light, 
the  less  steep  is  the  gradation  ; that  is,  if  a moderately 
quick  plate  allows  50  per  cent,  of  light  to  pass  with  an 
exposure  to  a certain  intensity  of  light,  and  5 per  cent, 
to  pass  with  another,  then  with  a quick  plate  this  ratio 
will  be  much  less  for  exposure  to  the  same  relative 
intensities  of  light.  A quick  plate,  then,  will  be 
much  more  capable  of  giving  the  necessary  gradation 
required.  One  winter  lately,  at  Rome,  the  writer  exposed 
two  brands  of  plates,  both  supposed  to  have  the  same 
rapidity,  on  the  same  subject.  With  the  one,  the 
highest  light  to  the  deepest  shadows  were  harmonious, 
and  the  details  in  all  parts  were  shown.  With  the 
other,  though  the  same  detail  was  to  be  found,  it  was 
not  printable  in  both  the  shadows  and  in  the  high- 
lights ; a careful  measurement  of  the  transparencies  of 
the  plates  when  exposed  in  artificial  and  in  daylight 
showed  that  for  camera  images  the  first  was  really  more 


INSTANTANEOUS  PHOTOGRAPHY.  69 

sensitive  than  the  second,  though  this  was  not  to  be  dis- 
covered by  the  artificial  light.  It  is  not  an  unfrequent 
complaint  that  is  made,  that  plates  which  give  a brilliant 
image  when  tested  by  the  latter  light,  will  often  give  a 
feeble  image  in  the  camera  which  nothing  seems  to 
avert.  Forcing  up  density  will  generally  induce  fog, 
and  this  is  to  be  avoided. 

Now  what  is  the  development  to  be  adopted  ? Per- 
sonally, the  writer  prefers  a thin  image,  full  of  detail, 
and  which  can  be  intensified  as  one  may  desire  ; and 
this  plan  is  one  which  he  adopts:  For  this  reason 

pyrogallic  acid  and  ammonia  development  are  avoided, 
for  though  the  image  may  appear  to  be  thin,  its 
appearance  may  be  deceitful,  for  if  it  have  that 
green  tint  which  is  so  often  characteristic  of  this 
development,  it  will  often  be  too  hard  to  give  a soft  and 
delicate  print,  though  if  it  were  a jet  black  deposit,  it 
would  be  too  thin.  A great  point  is  to  avoid  fog, 
and  notwithstanding  what  is  said  to  the  contrary,  it 
is  impossible  to  obtain  this  without  a fair  quantity  of 
alkaline  bromide  in  the  developer,  and  the  more  energetic 
the  developer,  the  more  bromide  there  will  be  required. 
One  thing  more,  however,  must  be  remembered,  which  is, 
that  a plate  made  with  a hard  gelatine,  or  a plate  in  which 
the  proportion  of  sensitive  salt  is  small  compared  with 
that  of  the  gelatine  enclosing  it,  will  require  less  bromide 
than  if  the  gelatine  is  soft,  or  if  the  sensitive  salt  is 
abundant.  With  this  in  view,  the  amount  of  bromide 
must  be  regulated.  In  most  formulae  for  the  new 
developers,  such  as  eikonogen  and  metol,  it  is  told  us 
that  no  bromide  is  required.  This  is  perfectly  true  with 
some  plates,  but  if  others  are  developed  without  it,  fog 


70 


INSTANTANEOUS  PHOTOGRAPHY. 


inevitably  will  result.  For  our  own  part,  we  like  either 
of  these  two  named  developers  for  the  purpose  in  view, 
for  the  deposit  is  black,  and  the  visual  and  photo- 
graphic transparency  of  the  different  parts  are  practically 
identical,  so  that  one  is  able  to  judge  by  the  eye  of 
what  one  may  expect  in  a print.  Besides  this  advantage, 
they  are  also  easy  to  work,  and  retain  their  developing 
powers  for  some  time  after  they  are  prepared. 


CHAPTER  XI. 


In  developing  rapid  plates,  care  should  be  taken  to  avoid 
an  over  strong  light  from  striking  on  them,  even  though 
it  be  of  what  is  considered  a safe  colour.  The  writer 
uses  a portable  lantern  in  a darkened  room,  the  diagram 
of  which  is  taken  from  “ Instruction  in  Photography.’^ 
It  was  first  introduced  by  Mr.  G.  S.  Edwards  in  a 
cylindrical  form,  but  it  is  more  convenient  when  modified 
to  the  following  shape. 


Fig.  26. 


A sheet  of  canary  paper  is  laid  upon  a sheet  of  orange 
paper,  and  the  two  sides  are  gummed  together  that  if 


72 


INSTANTANEOUS  PHOTOGRAPHY. 


spread  out  it  would  be  a cylinder  open  lop  and  bottom. 
It  is  then  folded  into  four  creases,  and  two  opposite 
ones  again  creased  in  the  middle.  When  placed  on  the 
table  it  presents  the  foim  as  shown  in  fig.  26.  An 
ordinary  bedroom  candlestick  can  be  placed  inside. 
The  top  is  covered  with  a shade,  as  shown  in  fig.  27, 


Fig.  27. 


to  screen  the  light  from  the  ceiling.  It  is  simply  a 
folded  quarter-sheet  of  thick  canary  paper.  This  lantern 
folds  up  perfectly  flat  in  its  creases,  and  can  be  placed 
in  a drawer,  or  at  the  bottom  of  the  portmanteau.  A 
small  window  giving  a brighter  light  can  be  made  in  one 
side  of  the  lantern  by  cutting  out  the  orange  paper,  the 
light  thus  passing  only  through  the  canary  paper.  In 
using  this  lantern  the  window  should  be  turned  away 
from  the  dish  in  which  development  takes  place,  the 
main  illumination  being  by  the  orange  light  coming 
through  both  papers.  When  daylight  is  used,  the 
window  is  best  blocked  out  with  opaque  paper,  except 
a couple  of  panes,  and  these  should  be  taken  out,  and 
stained  red  glass  inserted  in  their  place.  These  should 
be  covered  either  with  orange  paper  or  with  canary 
paper.  It  must  never  be  forgotten  that  plates  are  only 
insensitive  to  this  kind  of  light  when  the  exposure  to  it 
is  not  prolonged.  To  test  the  truth  of  this  assertion  a 
piece  of  a plate  may  be  covered  up,  and  the  remainder 
exposed  for,  say,  ten  minutes  to  the  light.  On  de- 
velopment the  covered-up  portion  will  remain  bright, 


INSTANTANEOUS  PHOTOGRAPHY. 


73 


-whilst  the  other  portion  will  show  signs  of  exposure. 
Por  this  reason  it  is  advisable  to  cover  up  the  dish 
during  development  by  a piece  of  card.  The  card  can 
be  removed  from  time  to  time  to  watch  the  progress  of 
the  image,  and  when  it  is  well  out  this  protection  may 
be  thrown  aside,  for  a plate  in  which  development  has 
proceeded  some  way  becomes  much  less  sensitive  than 
before  the  developer  has  been  applied.  Looking 
through  a negative  is  but  little  guide  to  the  true 
opacity  of  the  image,  as  it  is  so  loaded  with  unaltered 
silver  bromide. 

A word  or  two  of  warning  must  be  given  as  to  the 
colour  of  the  light  employed.  With  some  plates  the 
canary  paper  is  sufficient  protection,  but  with  others,  in 
which  a certain  amount  of  iodide  is  mixed  with  the 
bromide,  it  is  dangerous.  Again,  too,  the  orange  paper 
varies  in  hue.  There  is  one  which  is  redder  than  other 
brands.  When  examined  by  the  spectroscope  it  is 
found  that  some  blue  rays  pass  through  it.  If  the 
cover  of  this  book  be  taken  as  a sample  of  the  orange 
paper  used,  it  will  be  found  to  be  safe  in  every  respect. 

For  orthochromatic  plates  even  such  a light,  unless 
used  judiciously,  is  insecure,  since  they  are  sensitive  to 
the  colour  transmitted  through  orange  and  yellow.  For 
those  plates  which  are  only  sensitive  to  the  yellow,  a 
combination  of  ruby  glass  and  canary  medium  may  be 
taken  as  sufficiently  safe,  if  used  at  a respectful  distance. 
The  safest  light  is,  however,  a green  light,  such  as 
recommended  by  the  writer  in  1880  for  use  with  his  red 
sensitive  emulsion.  If  a lantern  be  glazed  with  a signal 
green  glass  and  a bottle  green  glass,  the  light  trans- 
mitted will  scarcely  affect  the  orthochromatic  plates 


74 


INSTANTANEOUS  PHOTOGRAPHY. 


sensitive  to  either  the  red  or  the  yellow,  since  it  lies  in 
that  part  of  the  spectrum  which  has  a minimum  effect 
on  them. 

The  light  of  a candle  filtered  through  such  glasses  is 
very  feeble,  and  plates  can  be  developed  in  it  free  from 
fog  if  the  precaution  of  covering  the  dish  is  not  neglected. 
With  plates  such  as  these  daylight  is  too  strong,  unless 
it  be  so  subdued  that  it  is  really  visually  feebler  than 
artificial  light. 

As  an  antithesis  to  this  it  may  be  said  that  any  plate 
may  be  developed  in  naked  candle  light,  and  yet  be  free 
from  fog,  if  the  candle  be  placed  far  enough  off,  and  it 
be  so  arranged  that  the  light  is  not  reflected  from  a white 
ceiling  or  light-coloured  walls.  The  most  rapid  plate, 
exposed  for  ten  seconds  to  a naked  candle  forty  feet  off, 
and  fully  shining  on  it,  shows  no  signs  of  exposure.  A 
plate  might  be  exposed  to  this  light  during  transferrence 
to  the  developing  dish,  and  whilst  it  is  being  covered 
with  the  developer,  and  still  show  no  signs  of  fog  if  it 
be  covered  up  during  the  initial  stage  of  development. 
The  great  point  is  for  a photographer  to  know  what  he 
can  and  what  he  can’t  do,  and  this  is  one  of  the  things 
that  he  should  know,  as  it  may  be  of  use  to  him. 

It  is  to  be  remembered  that  the  same  kind  of  light  in 
which  development  may  take  place  should  be  employed 
for  changing  the  plates. 


CHAPTER  XII. 


The  predilection  of  the  writer,  which  was  stated  at  the 
end  of  Chapter  X.,  as  to  the  developer  to  use,  must  not 
bias  the  readers,  for  certainly  other  workers  obtain  results 
with  pyrogallic  acid  which  leave  nothing  to  be  desired. 
Formulae  which  are  recommended  are  therefore  given. 
The  formula  which,  perhaps,  is  able  to  bring  out  most 
detail  is  that  recommended  originally  by  the  late  Col. 
Stuart  Wortley.  By  his  plan  the  plate  is  first  soaked  for 
a couple  of  minutes  in  dilute  ammonia,  and  then  the 
bromide  and  pyrogallic  acid  are  added  subsequently, 
little  by  little,  till  proper  density  is  obtained. 

The  formula  stands  thus  — 

No.  I. 

Ammonia  . . . . . . . . i drachm 

Water  . . . . . . • • 9 drachms 

No.  2. 

Pyrogallic  acid  (dry). 

No.  3. 

Sulphite  of  soda  (a  saturated  solution). 

No.  4. 

Potassium  bromide  . . . . 20  grains 

Water 


I ounce 


76  INSTANTANEOUS  PHOTOGRAPHY. 

One  drachm  of  No.  i is  mixed  with  2 ounces  of  water, 
and  the  j?iate  is  flooded  with  this  till  the  film  is  saturated 
with  it;  I drachm  of  No.  4,  i drachm  of  No.  3,  with 
ij-  grains  of  No.  2,  are  placed  in  the  developing  glass. 
The  ammonia  is  poured  back  again,  and  the  mixed 
developer  is  applied.  The  development  is  continued 
till  the  image  appears  well  at  the  back  of  the  plate,  or 
if  it  lags,  more  of  Nos.  2,  3,  and  4 are  added  till  this 
result  is  obtained.  With  this  development  it  is  well  to 
use  alum,  as  the  film  is  apt  to  get  loose  on  the  glass. 
After  washing,  it  is  therefore  placed  in  a 7 or  8 per  cent, 
solution  of  alum.  It  is  again  well  washed,  when  it  is 
placed  in  the  usual  fixing  bath — 

Hyposulphite  of  soda  . . . . i ounce 

Water  . . . , . . . . 6 ounces 

It  is  again  thoroughly  washed,  and  the  density  examined. 
If  too  weak,  it  may  be  at  once  intensified  by  one  or 
other  of  the  methods  which  are  at  present  extant  (see 
next  Chapter). 

Two  drachms  of  a 10  per  cent,  solution  (50  grains  of 
the  salt  to  i ounce  of  water)  of  carbonate  of  soda  may 
be  substituted  for  the  drachm  of  No.  i,  as  given  above. 
In  this  case  we  have  an  alkaline  solution,  which  is  not 
liable  to  lose  strength  through  evaporation.  Many 
photographers  like  this  better  than  the  ammonia  on 
this  account. 

Perhaps  the  developer  which,  when  used  as  a one- 
tluid  ’’  developer,  brings  out  more  detail  in  a shorter 
time  than  any  other,  is  the  metol  developer,  and  this 
can  be  employed  in  nearly  every  case  where  exposure 
within  proper  limits  is  employed.  It  is  energetic  and 


INSTANTANEOUS  PHOTOGRAPHY.  77 

quick  acting,  but  if  it  errs  at  all,  it  errs  in  not  giving 
quite  enough  density. 

It  should  be  made  as  follows  : — 


Metol  c . . . . . . . 8 grains 

Sulphite  soda  . . . . . . 50  ,, 

Carbonate  of  soda.  . . . . . 50  ,, 

Bromide  of  potassium  . . . . ^ grain 

Water  . . . . . . . . 2 ounces 


This  developer  is  very  rapid  in  its  initial  action,  and  the 
image  is  a phantom  one  at  first.  In  case  it  appears  too 
rapidly,  the  action  should  be  stopped  by  washing  the 
plate,  and  applying  a (20  grains  to  the  ounce  of  water) 
solution  of  bromide  of  potassium.  Density  may  be 
obtained  by  again  washing,  and  applying  a solution  of 
pyrogallic  acid  (3  grains  to  the  ounce  of  water),  and 
developing  as  usual.  There  will  be  just  sufficient  alkali 
left  in  the  film  to  allow  a reduction  of  silver  on  those 
parts  on  which  a deposit  had  taken  place,  this  allowing 
good  density  to  be  attained. 

A very  favourite  developer  with  the  writer  is  the  amidoL 
The  image  appears  very  rapidly  at  first,  and  gradually 
obtains  density.  It  is  a mistake  to  hurry  in  develop- 
ment. The  image  should  appear  well  at  the  back  of 
the  plate  if  printing  density  is  to  be  obtained.  It  can. 


be  made  as  follows  : — 

Amidol 

5 grains 

Sodium  sulphite  . . 

40 

Potassium  bromide 

I grain 

Water 

2 ounces 

This  solution  will  keep  a few  days,  but  is 

most  energetic 

when  used  fresh.  Both  this  and  the  metol  may  be  used 

78 


INSTANTANEOUS  PHOTOGRAPHY. 


for  a good  number  of  plates  ; 6 oz.  of  either  should 
develop  twenty-four  quarter-plates,  using  the  fresh  solu- 
tion for  those  which  were  suspected  of  being  barely 
exposed  sufficiently. 

Before  development  is  commenced  the  plate  should 
be  thoroughly  brushed  over  with  a soft  dry  brush.  (The 
word  dry  is  italicized  because  so  often  the  brush  is  left 
carelessly  about.)  Before  the  plate  is  taken  out  of  the 
slide  and  put  into  the  dish,  the  developing  solution 
should  be  ready  at  hand  to  prevent  an  access  of  light  to 
it.  The  solution  should  be  evenly  applied,  and  cover 
the  plate  at  once.  If  it  stop  in  its  flow  there  will  be  a 
great  probability  of  markings  showing  on  the  finished 
negatives.  There  are  many  kinds  of  dishes  in  the 
market  at  the  present  time.  There  are  none  which  are 
better  than  the  celluloid  for  travelling,  though,  for  some 
work,  good  flat  white  dishes  about  inches  in  depth 
are  to  be  preferred  for  cleanliness  sake.  It  is  always  as 
well  to  avoid  putting  the  fingers  in  the  developer  if 
possible,  and  if  the  end  of  an  ordinary  wooden  match 
be  cut  to  a wedge  shape,  this  will  lift  the  plate  out  of 
the  solution  readily,  when  it  can  be  seized  by  the  hands 
and  examined  as  required.  A similar  one  may  be  used 
for  the  fixing  bath,  but  the  same  one  should  not  be  used 
for  the  developing  solution  as  well  as  the  fixing  solution, 
for  hyposulphite  of  soda,  even  in  small  quantities,  is  not 
a desirable  addition  to  most  developers. 


CHAPTER  XIII. 


The  most  perfect  intensification  is  carried  out  by  the 
plan  which  was  introduced  by  Mr.  Chapman  Jones,  but 
in  the  writer’s  experience  it  has  to  be  carefully  carried 
out,  or  success  will  be  wanting. 

In  the  first  place,  all  hyposulphite  must  be  got  rid  of. 
If  the  washing  be  not  complete,  steps  must  be  taken  to 
remove  any  trace  of  it.  The  writer  himself  prefers  a solu- 
tion of  hydroxyl,  since  it  readily  attacks  hyposulphite, 
without  effecting  any  decomposition  of  the  silver.  If  a 
solution  of  hydroxyl  be  obtained  it  may  be  diluted — 
2 0 parts  to  I — and  the  plate  immersed  in  it  for  a 
quarter  of  an  hour.  Failing  this,  another  application 
• of  the  alum  bath  may  be  given,  or  a very  dilute  solution 
(i  in  200)  of  hydrochloric  acid.  This  last  will  effectually 
remove  the  hyposulphite.  The  plate  is  then  washed, 
and  immersed  in  a saturated  solution  of  mercuric 
chloride  (bichloride  of  mercury),  to  each  ounce  of  which 
a drop  of  strong  hydrochloric  acid  has  been  added, 
until  the  whole  of  the  silver  is  converted  into  a white 
substance,  which  is  a double  chloride  of  mercury  and 
silver.  The  acid  prevents  the  formation  of  a compound 
which  is  prejudicial  in  subsequent  operations.  The 


8o 


INSTANTANEOUS  PHOTOGRAPHY. 


film  is  next  thoroughly  washed.  The  washing,  if 
possible,  should  take  place  in  running  water,  and  con- 
tinue for  a quarter  of  an  hour,  or  until  the  white  surface 
begins  to  get  a little  brown  from  the  alkaline  carbonates- 
which  are  to  be  found  in  most  waters.  It  is  not  a bad 
plan,  when  many  negatives  have  to  be  washed,  to  make 
a shallow  trough  just  the  width  of  the  plate,  and  which 
will  hold  half-a-dozen  at  a time.  The  trough  is  filled 
with  the  plates,  and  placed  at  a gentle  slope  under  the 
water  supply.  The  stream  of  water  will  thus  pass  over 
each  negative  in  succession,  and  the  whole  number 
will  be  washed  at  one  time.  When  the  washing  is 
complete  the  plates  are  immersed  in  a solution  of 
ferrous  oxalate,  which  is  prepared  as  follows  : — 

A. 

Ferrous  sulphate  . . A saturated  solution. 

B. 

Potassium  oxalate  . . A saturated  solution. 

One  part  of  A is  poured  into  4 parts  of  B,  and  the 
resulting  red  liquid  is  ferrous  oxalate  in  solution  mixed 
with  potassic  sulphate,  an  inert  body  as  far  as  the 
developer  is  concerned.  This  is  applied  to  the  bleached 
plate  in  ordinary  daylight,  and  after  some  considerable 
time  the  white  film  at  its  upper  surface  becomes  black, 
and  finally  the  same  hue  is  taken  by  the  particles  next  the 
back  of  the  plate.  When  this  occurs  the  intensification 
is  complete.  The  plate  may  then  be  washed  and  dried  ;* 
but  with  most  waters,  if  this  be  done  without  any  inter- 
mediate bath,  the  plate  takes  markings  somewhat  like- 
watered  silk,  due  to  the  formation  of  insoluble  oxalate 
of  lime  caused  by  the  decomposition  of  the  potassium^ 


INSTANTANEOUS  PHOTOGRAPHY. 


8l 


oxalate  by  the  carbonate  of  lime  in  the  water.  The 
writer’s  practice  is  to  soak  the  plate  for  some  five  minutes, 
after  washing,  in  dilute  hydrochloric  or  citric  acid,  which 
-decomposes  this  oxalate  of  lime,  when  it  may  be  rinsed 
well,  and  set  up  to  dry.  A couple  of  washes  of  distilled 
water  after  bleaching,  and  after  the  application  of  the 
ferrous  oxalate,  will  answer  as  well  as  the  above  acid 
•solution.  If  any  hyposulphite  have  been  left  in  the  film, 
yellow  stains  are  liable  to  appear  in  what  should  be 
the  transparent  parts,  and  the  same  happens  if  the 
mercuric  chloride  which  is  not  in  combination  with  the 
•silver  has  failed  to  be  removed. 

This  method  of  intensification  is  such  as  to  about 
-double  the  visual  opacity  of  the  film  for  the  half-tones, 
.and  it  has  the  advantage  that  it  may  be  repeated  till 
.any  desired  density  is  arrived  at. 

The  other  method  of  intensification  is  by  means  of 
•cyanide  of  silver  following  on  the  bleaching  by  chloride 
of  mercury.  It  may  be  remarked  that  for  bleaching 
for  this  last  method,  some  prefer  to  employ  mercuric 
bromide.  This  is  obtained  by  mixing  with  the  mercuric 
•chloride,  potassium  bromide,  mercuric  bromide  and 
potassium  chloride  being  formed. 

The  formula  for  bleaching  is  as  follows  : — 


Mercuric  chloride . . 

Potassium  bromide 
Water 

And  for  blackening  the  deposit : — 
Nitrate  of  silver  . . 

Water 


100  grains 
100  „ 

10  ounces 

100  grains 
10  ounces 


To  this  silver  solution  is  added  cyanide  of  potassium 


82 


INSTANTANEOUS  PHOTOGRAPHY. 


(which  is  a deadly  poison)  in  sufficient  quantity  to  very 
nearly  but  not  quite  dissolve  the  cyanide  of  silver  first 
formed. 

It  is  convenient  to  make  a solution  of  loo  grains  of 
cyanide  of  potassium  to  the  ounce  of  water,  and  add  it 
gradually  till  this  end  is  obtained.  This  intensification, 
is  most  effective  when  the  negative  has  been  dried. 
It  is  first  bleached  in  the  mercury  solution,  when  it  is 
taken  out  and  washed  for  half-an-hour.  It  is  then 
placed  in  the  cyanide  of  silver  solution  till  the 
bleaching  at  the  back  of  the  film  gives  place  to  a. 
black. 

The  deposit  is  a beautiful  black  by  this  method,, 
and  consists  chiefly  of  a double  cyanide  of  silver  and 
mercury.  If  left  too  long  in  the  last  bath,  intensity 
diminishes  again,  owing  to  the  cyanide  of  mercury 
being  slightly  soluble  in  the  bath. 

If  with  this  intensification  the  negative  is  too  dense,, 
it  can  be  reduced  as  much  as  needs  be  by  immersing  it 
in  a dilute  solution  of  sodium  hyposulphite  (20  grains- 
to  the  ounce).  The  whole  of  the  intensity  can  be  taken 
away  by  strong  hyposulphite,  but  the  action  can  be 
arrested  at  any  time  by  taking  it  out  of  the  weak  solution 
and  washing.  The  intensified  negative,  when  dry,  is  a- 
little  less  intense  than  when  wet.  The  atmosphere  is- 
apt  to  attack  the  intensified  images,  giving  them  an 
appearance  of  sulphurisation,’’  and  when  the  right 
density  is  secured  it  is  well  to  varnish  them  with  ordinary 
negative  varnish.  Careful  washing  is  as  necessary  in  this- 
process  as  it  was  in  the  preceding. 

The  writer  has  recently  used  intensification  by  bleach- 
ing alone,  without  attempting  to  blacken  the  deposit. 


INSTANTANEOUS  PHOTOGRAPHY.  8 5 

The  formula  used  is  that  given  above,  where  bromide 
of  mercury  is  shown  as  the  active  reagent. 

The  question  comes  as  to  when  sufficient  density  is- 
secured,  either  in  the  simply  developed  or  in  the  inten- 
sified negative.  Of  course  it  will  be  said  that  to  take 
a print  from  it  is  the  easiest  way  to  ascertain  this,  and,, 
no  doubt,  for  the  inexperienced,  this  is  an  excellent  way 
of  deciding ; but  it  often  happens  that  a decision  has  to- 
be  made  when  the  appliances  for  printing  are  not  at  hand. 

It  is  a curious  fact,  which  is  confirmed  by  others 
besides  the  writer,  that  the  judgment  is  apt  to  be 
misled,  when  away  from  one’s  ordinary  dark  room,  as 
to  the  opacity  a negative  should  show.  For  instance,, 
in  taking  and  developing  a series  of  views  on  tour,  a 
good  deal  depends  on  the  quality  of  negative  obtained 
during  the  first  day  as  to  the  standard  of  density  that  is 
looked  for.  These  may  often  be  really  too  weak,  but  it 
will  very  often  happen  that  they  will  be  thought  good 
for  printing,  and  the  remainder  will  be  standardised 
accordingly.  It  is  a very  useful  guide  to  take  with  one  on 
tour  a good  printing  negative,  and  from  time  to  time  to- 
compare  visually  the  developed  negatives  with  it.  It 
must  be  recollected  that  an  opacity  in  the  high  lights 
beyond  that  necessary  to  give  a white  in  a print,  when 
the  bare  glass  gives  the  deepest  black,  is  detrimental 
a negative  carried  beyond  that  opacity  will  give  a harsh 
print  as  a rule,  and  lack  that  quality  which  will  enable 
gradation  in  whites  to  be  shown,  when  the  gradation  in 
the  blacks  is  also  rendered — in  other  words,  a harsh 
print  will  be  produced.  In  instantaneous  photography 
there  is  always  a tendency  to  this  by  the  tyro,  generally 
through  an  endeavour  to  give  too  short  an  exposure. 


^4  INSTANTANEOUS  PHOTOGRAPHY. 

The  most  opaque  part  of  the  negative — except,  per- 
haps, minute  spots  illuminated  by  sunlight,  and  almost 
specularly  reflected  on  to  the  lens— should  not  have  a 
greater  opacity  than  that  which  allows  eV  to  yV  of  the 
light  to  pass  through  it.  Thus,  for  instance,  if  the 
deepest  shadow  be  represented  as  bare  glass,  the  opacity 
(the  brightest  part)  of  a white  cloud  illuminated  by  full 
sunlight  should  not  show  more  than  that  density  if  sky 
and  landscape  are  to  be  rendered  in  the  print. 

The  method  of  making  a scale  of  shade  has  been 
shown  in  a previous  chapter,  and  it  will  suffice  to  have 
such  an  one,  and  print  it,  say,  in  platinum,  but  printing 
so  that  the  bare  glass  shall  attain  the  deepest  black 
possible,  and  then  to  note  which  is  the  first  opaque  part, 
where  no  action  is  apparent  when  compared  with  the 
whiteness  of  the  unexposed  platinum  paper.  This  can 
-easily  be  done  by  placing  in  the  printing  frame,  between 
the  negative  and  the  platinum  paper,  a strip  of  black 
paper  along  it,  masking  a portion  of  the  various  grada- 
tions obtained.  The  opacity  which  indicates  this 
equality  in  whiteness  is  noted,  and  the  greatest  opacities 
of  the  negative  can  be  compared  with  it  in  a very  ready 
manner.  Make  two  or  three  fine  ink  dots  on  a piece  of 
white  paper,  and  the  eye  will  judge  of  the  distinctness 
of  them  when  seen  through  the  particular  part  of  the 
scale  of  shade  which  was  marked.  The  same  dots  are 
then  viewed  through  the  most  opaque  parts  of  the 
negative,  and  a judgment  is  rapidly  formed  of  the  opacity 
of  its  deposit.  One  can  estimate  relative  opacities  to 
within  5 per  cent,  by  this  plan  with  a little  practice. 

There  are  methods  which  can  accurately  measure 
these  differences  in  opacity,  one  of  which  is  given  in 


INSTANTANEOUS  PHOTOGRAPHY. 


85 


‘‘  Instruction  in  Photography/’  and  as  it  is  measured 
under  the  same  conditions  in  which  a print  is  taken^ 
it  is  very  trustworthy ; but  for  purposes  of  judging 
density  approximately,  the  above  plan  is  sufficiently 
accurate.  The  writer  would  then  recommend  that  a 
graduated  scale  be  prepared,  as  given  at  page  53,  and  a 
strip  of  such  containing  the  various  opacities  taken  as 
a guide.  It  may  be  remarked  that  a scale  of  opacity 
prepared  on  a celluloid  film  is  convenient,  as  it  can  be 
carried  without  any  fear  of  damage  or  breakage.  The 
writer  carries  one  such  in  his  pocket-book. 

Of  course,  what  has  been  said  regarding  the  opacity 
needful  must  be  taken  only  as  a general  rule.  Particular 
cases  require  particular  treatment.  Thus  if  the  beauty 
of  a view  consists  in  getting  detail  and  force  in  what 
would  be  the  half-tones  ordinarily,  the  sky  must  be 
sacrificed,  and  become  a blank,  as  far  as  gradation  is 
concerned,  and  the  unsatisfactory  expanse  of  white  paper 
representing  it  be  filled  in  by  double  printing  from  a cloud 
negative.  This  is  recommended  by  many  excellent 
photographers,  but  does  not  appeal  to  the  present 
writer  as  desirable.  This,  however,  is  merely  a matter 
of  opinion  for  which  no  one  person  must  be  held 
responsible.  The  ideas  of  what  is  artistic  are  so  varied^ 
and  the  methods  of  arriving  at  them  so  different,  that  it 
would  be  a bold  man  to  lay  down  any  fixed  rule  con- 
cerning any  one  plan.  From  a scientific  point  of  view,, 
however,  the  method  of  double  printing  seems  a depar- 
ture from  attaining  that  truth  at  which  photographers- 
should  aim. 


CHAPTER  XIV. 


A FEW  words  must  be  said  on  choosing  a view  with  a 
Eand-camera.  There  is  no  doubt  that  a photograph 
should  embrace  that  part  of  the  general  view  which 
appeals  most  to  the  eye ; but  it  must  be  recollected 
that  in  the  appeal  to  the  eye,  its  training  should  be  such 
that  the  view  is  divested  of  colour  in  thought.  Probably 
a very  fair  estimate  of  a view  is  obtained  by  looking  at 
it  through  a greenish  blue  glass,  which  cuts  off  the  red 
and  the  yellow  rays,  and  leaves  it  approximately  a 
monochrome.  Colour  is  very  often  deceptive,  particu- 
larly in  spring  and  autumn.  The  eye  will  see  colours 
contrasted  with  one  another,  and  it  is  these  contrasts 
alone  which  have  a real  pictorial  value,  the  composition 
playing  almost  a secondary  part.  Divested  of  colour, 
a view  such  as  this,  when  photographed,  must  be 
necessarily  disappointing;  but  a glance  through  a medium 
such  as  that  recommended  will  at  once  tell  us  what  to 
expect.  Constant  practice  will,  however,  enable  one  to 
•do  without  this  aid,  and  when  such  experience  has  been 
arrived  at  it  is  a relief.  The  view-finder  attached  to  a 
camera  is  an  excellent  device,  and  certainly  every 
beginner  should  have  one  attached  to  his  hand-camera ; 


INSTANTANEOUS  PHOTOGRAPHY. 


87 


iDut  here  again  it  is  unnecessary  to  the  experienced 
operator.  His  training  enables  him  to  judge  of  the 
angle  of  view  which  his  camera  will  take  horizontally 
and  vertically,  and  if  a couple  of  lines  be  ruled  on  the 
top  of  it,  showing  the  angle  included,  he  will  rarely  make 
a mistake.  He  can  then  point  his  camera  in  the 
direction  required,  and  attend  to  that  indispensable 
adjunct  to  it — viz.,  the  spirit  level,  which  will  tell  him 
not  only  whether  his  camera  is  level,  but  will  also 
indicate  to  him  when  it  is  steady  enough  to  make  an 
exposure.  But  if  a view-finder  has  to  be  used — and  in 
nine  cases  out  of  ten  it  should — the  great  point  is  to 
have  a suitable  one  which  can  be  readily  inspected  even 
in  brilliant  sunshine.  There  are  various  kinds  in  the 
market,  but  none  seem  better,  or  so  good,  as  that  made 
on  the  principle  of  the  magnifying  glass,  in  which  an 
image  is  formed  by  one  small  lens,  and  vertically  looked 
at  through  a fixed  magnifying  lens,  the  image  being 
reflected  by  a mirror  upwards.  In  this  instrument 
there  is  no  movement  of  the  image  when  the  eye  is 
moved,  as  is  the  case  when  the  finder  is  a concave 
mirror.  The  view  can  be  seen  in  the  brightest  sunlight, 
which  is  not  the  case  when  the  images  are  viewed  on  a 
ground  glass,  even  when  shaded  by  a hood. 

The  view  having  been  seen  in  the  view-finder, 
whatever  is  used,  the  eye  should  at  once  take  in  the 
position  that  the  bubble  of  the  level  occupies  ; and  here 
let  it  be  said  that  the  circular  spirit  level  is  better  than 
two  straight  levels  placed  at  right  angles  to  one  another, 
as  with  it  only  one  bubble  has  to  be  watched,  while  in 
the  latter  cas.e  the  position  of  two  has  to  be  taken  in  by 
the  eye.  It  is  probable,  when  the  bubble  is  central,  that 


88 


INSTANTANEOUS  PHOTOGRAPHY. 


there  will  be  too  much  foreground,  in  which  case  the 
rising  front  of  the  camera  must  be  used  to  cut  oif  a 
portion,  and  a little  practice  will  tell  the  operator  how 
much  of  that  seen  in  the  finder  will  disappear,  and  ho\Y 
much  of  the  sky  be  added.  The  appearance  of  the 
image  will  also  be  a good  guide  as  to  the  stop  to  be 
used,  and  of  the  speed  to  which  the  shutter  should  be 
set.  If  a small  neutral-tinted  graduated  image  be 
interposed  between  the  eye  and  the  image,  and  the 
brilliancy  be  diminished  till  it  has  a brilliancy  to  which, 
one  is  accustomed,  these  may  be  arrived  at  with  great 
certainty ; but,  as  before  said,  it  is  better  to  alter  the 
stop  rather  than  the  speed  of  the  shutter.  Of  course  it 
is  not  necessary  with  every  view  to  take  these  measures, 
otherwise  a passing  effect  would  often  be  lost. 

A golden  rule  to  carry  out  always  is,  as  far  as  possible, 
keep  the  camera  level,  and  use  the  rising  front  if 
necessary.  Dismiss  all  colour  from  the  mind,  and  have 
some  one  point  of  interest  in  the  view.  The  writer  has 
often  seen  excellently  taken  views,  each  of  which  would 
have  cut  up  into  two  and  sometimes  three  views,  each 
of  which  would  have  been  complete  in  itself.  Have 
some  dark  points  as  well  as  light  points  in  the  composi- 
tion, for  one  will  help  the  other.  If  there  are  none  of 
the  former,  the  print  will  be  flat  and  washy.  In 
instantaneous  work,  as  in  any  other  photography,  if  loo- 
plates  are  exposed,  don’t  label  all  as  excellent. 
Technically,  perhaps,  nine  out  of  ten  may  be  good, 
but  probably  of  these  nine,  five  or  six  should  be 
Avashed  off. 

The  small  sized  plates  cost  but  little,  and  there  is  an 
inclination  to  “ let  off”  a-many.  This  is  very  good  for 


INSTANTANEOUS  PHOTOGRAPHY. 


89 


the  plate  makers,  but  fatal  for  the  education  of  the 
photographer.  A view  should  be  every  bit  as  carefully 
selected  as  if  a camera  or  a stand  were  being  used,  and 
time  exposure  given ; and  these  snap-shots,  exposed 
almost  for  pure  “ cussedness,”  are  to  be  reprobated. 
The  Chancellor  of  the  Exchequer  would  reap  a handsome 
amount  if  he  taxed  every  snap-shot  made  to  no  purpose. 
The  thing  to  do  is  to  think  over  the  view,  and,  when 
thought  over,  to  make  the  best  possible  picture  out  of 
it.  These  are  views  which  will  not  meet  with  approval 
by  many,  but  they  are  recorded  as  a deliberate  expression 
of  opinion. 


CHAPTER  XV. 

There  is  a kind  of  instantaneous  photography  which, 
however,  is  not  dependent  on  a shutter,  and  that  is 
ivhere  the  illumination  itself  is  instantaneous,  or  rather, 
perhaps,  it  should  be  said,  of  short  duration.  That  «• 

with  which  photographers  are  most  familiar  is  the  ^ 

‘‘  magnesium  flash-light,’’  where,  as  the  name  denotes,  ^ 

the  light  is  produced  by  burning  magnesium  in  powder.  ' 

We  may  have  a colourless  flame,  say,  of  a spirit  lamp,  ; 

and  by  some  means  or  another  cause  the  powder  to  3 

cross  it ; the  heat  is  sufficient  to  effect  the  ignition  of  1 


the  magnesium,  and  the  production  of  a momentary  ’ 

intensely  bright  light.  Experiments  have  been  made  i 

by  the  writer  to  ascertain  the  photographic  value  of  the  J 

light  caused  by  the  burning  of  a grain  of  magnesium  | 

compared  with  that  of  the  electric  light.  In  a com-  ^ 

munication  to  the  Camera  Club,  in  1891,  he  gave  the  j 

details  of  these  experiments,  and  we  need  only  give  an  ^ 

extract  as  to  the  results  obtained.  It  was  found  that  | 

I grain  of  magnesium  burnt  was  equal  to  2*16  candles  ^ 

of  the  whiteness  of  the  electric  arc  light,  burning  for  2 

one  minute,  as  an  illuminant.  Sunlight  may  be  taken 
roughly  as  twice  that  of  the  electric  light  for  each 


INSTANTANEOUS  PHOTOGRAPHY. 


91 


visual  candle,  and  is  thus  approximately  that  i grain 
of  magnesium  is  equal  to  the  photographic  value  of 
about  one  visual  candle  of  sunlight  acting  for  one  minute. 
As  there  are  about  5,000  visual  candles  in  sunlight,  if 
such  a number  could  be  placed  one  foot  from  a screen  (at 
which  distance  the  magnesium  was  also  burned),  it 
follows  that  5,000  grains  of  magnesium,  burned  at  one 
foot  distance  from  an  object,  would  equal  the  photo- 
graphic illumination  of  sunlight  acting  for  one  minute — 
that  is,  if  a piece  of  platinum  paper  were  exposed  for  one 
minute  to  the  sun,  the  same  blackness  on  development 
would  be  produced  by  igniting  5,000  grains  of  magnesium 
at  one  foot  from  it.  To  produce  a good  instantaneous 
picture  in  sunlight  we  may  take,  perhaps,  the  w of  a 
second,  with  a stop  of  y/32,  as  necessary,  and  the 
equivalent  of  that  would  be  s-oVtt  of  5,000  grains,  or  f of 
a grain,  or  1*67  grains  of  magnesium  burnt  at  one  foot  off. 
If  we  place  the  object  ten  feet  off,  we  should  require  100 
times  as  much,  or  about  170  grains.  For  flash-light 
work  a lens  working  with  //8  may  be  used  with 
advantage,  in  which  case  we  should  only  require  the  iV 
of  that  quantity,  or,  say,  10  grains.  It  will  be  noticed 
that  no  mention  is  made  of  the  time  of  exposure  with 
the  magnesium.  It  matters  very  little  whether  the 
-exposure  last  a long  or  a short  time  ; the  only  requisite 
is  that  the  necessary  amount  of  magnesium  should  be 
burnt.  As  a matter  of  fact,  the  duration  of  a flash 
varies  very  much,  but,  as  a rule,  it  lasts,  when  i o grains 
are  burnt  in  a proper  lamp,  about  the  one-eighth  of  a 
second.  The  diagram  (Fig.  28,  page  92)  shows  the 
measure  of  a flash.  A plate  was  rotated  about  once  in 
the  one-fourth  of  a second  in  front  of  a small  hole  cut 


92 


INSTANTANEOUS  PHOTOGRAPHY. 


in  a card.  A sector  with  only  four  apertures  was 
caused  to  rotate  in  front  of  the  hole,  and  the  flash  im- 
pressed the  plate  as  shown.  The  effective  part  of  the- 
flash  occupied  only  eleven  intervals  of  the  passage  of  the 
apertures  of  the  sector  in  front  of  the  hole,  and  as  the 
speed  of  rotation  was  20  times  a second,  80  apertures, 
passed  per  second  ; the  total  effective  exposure  was,. 


Fig.  28. 


therefore,  of  a second,  say  i of  a second.  This- 
quantity  of  magnesium  is  sufficient  to  photograph  an 
object  10  feet  off  when  the  light  is  judiciously  reflected,, 
and  the  exposure  in  this  case  would  be  about  one-eighth 
of  a second.  By  connecting  two  or  more  lamps 
together  by  rubber  tubing,  and  placed  at  different 
distances  so  as  to  break  up  the  shadows,  and  sending 
the  magnesium  through  each  flame  at  the  same  instant — 


INSTANTANEOUS  PHOTOGRAPHY. 


93 


Avhich  is  effected  by  the  india-rubber  tubes  being  con- 
nected— the  lighting  is  better,  and  results  can  be  obtained 
which  are  not  to  be  despised  as  artistic  productions. 

We  may,  however,  employ  the  spark  from  a battery 
•of  Leyden  jars  for  a certain  class  of  photographs ; for 
instance,  when  we  wish  to  photograph  waves  of  sound 
or  falling  drops  of  water.  The  arrangement  for  this  is 
very  simple  : — 


Fig.  29. 


The  knobs  A A of  the  spark  apparatus  are  connected 
with  Leyden  jars,  which  can  be  charged  by  a Wimshurst 
or  other  electric  machine.  The  lens  Li  is  placed  to 
■condense  the  spark  and  cast  its  image  on  the  centre  of 
the  camera  lens  L2.  This  causes  a disc  of  light  to 
fall  on  P,  the  plate,  where  the  spark  passes.  The 
object  O,  which  is  to  be  photographed,  is  focussed 
on  to  P.  In  case  of  a moving  object,  the  appearance  it 
has  when  the  spark  passes  is  photographed  within  the 
illuminated  disc.  The  amount  included  depends  on 
the  diameter  of  Li  and  the  closeness  of  O to  Lj.  Or  a 
•stream  of  falling  water  may  be  photographed,  and  the 
•separation  into  drops  will  be  well  shown.  There  are, 
in  fact,  an  endless  variety  of  scientific  experiments 
which  may  be  carried  out  by  this  means. 

For  some  purposes  the  simple  shadow  method  may 
Le  employed  in  the  way  that  Lord  Rayleigh  and  Prof. 
Toys  have  carried  out  so  successfully.  No  lens  is 


94 


INSTANTANEOUS  PHOTOGRAPHY. 


employed,  but  the  object  whose  shadow  is  to  be  depicted 
is  caused  to  fall  or  move  near  the  plate,  an  exposure  is- 
made  by  the  spark,  and  it  being  practically  a point,  the* 
shadow  images  are  fairly  sharp  and  defined.  The 
writer  prefers  the  camera  method  to  this  last,  since  it 
prevents  the  difficulty  of  exposing  in  a dark  room. 
The  definition,  too,  is  better.  The  drawback  to  the 
camera  method  is  that  it  is  limited  to  the  movement 
which  takes  place  within  the  area  of  the  condensing 
lens  Li.  The  accompanying  diagram  gives  the  positionv- 
of  bubbles  of  air  blown  in  a cell  of  water. 


Fig.  30. 

For  opaque  objects  the  spark  light  may  be  condensed! 
in  a circle  by  means  of  on  the  object,  and  the  camera 
be  placed  alongside  the  discharging  knobs  A A.  It  is^ 
needless  to  say  that  the  illumination  is  very  inferior  to- 


INSTANTANEOUS  PHOTOGRAPHY.  95 

that  obtained  by  the  method  shown  in  the  figure,  and 
may  not  always  be  successful.  The  time  of  exposure 
is  certainly  less  than  the  TuirVoxr  of  a second  in  this> 
case.  A disc  with  a clean  cut  series  of  holes  four 
inches  from  the  centre  was  rotated  8o  times  a second,, 
and  the  spark  exposure  given  to  it,  a sensitive  photo- 
graphic plate  being  placed  behind  it.  The  velocity  of 
each  hole  was  thus  about  2,000  inches  per  second.  A 
movement  during  the  time  of  exposure  equal  to  the 
To  o-th  of  an  inch  would  easily  have  been  recognised,. 
but  each  hole  was  shown  perfectly  sharp  : the  time 
during  which  the  spark  lasted  was  therefore  less  than 
^ooVoo  of  a second,  so  that  the  limit  above  stated  is. 
certainly  under  the  mark. 

These  remarks  as  to  flash-light  and  spark  photo- 
graphy have  only  been  given  as  suggestive,  and  must 
not  be  considered  by  any  means  as  a complete  descrip- 
tion of  them. 


WEIGHTS 


AND 


MEASURES 


1 Sovereign  weighs... 

I Shilling  „ 

48  Pence  „ ...  

Half-penny  and  Three-penny  piece  weigh 

Florin  and  Sixpence  ...  

Three  Pennies  

4 Half-crowns  and  I Shilling 
4 Florins,  4 Half-crowns,  2 Pennies 
I Half-penny  = i inch  in  diameter. 


. 123  274  grains 
. 87-273  _ „ 

. I lb.  avoirdupois 
. 5 ounce 

1 

• ¥ >1 

• I 

. 2 ounces 

• 4 ,, 


Grains  ... 
16  Drachms 
16  Ounces  ... 


^4  Grains 
20  Pennyweights 
12  Ounces 


Avoirdupois  Weight. 

I drachm  (=  27^4  grains) 

I ounce  (=  4371  „ ) 

I pound  (=  7000  „ ) 

Troy  Weight. 

...  i pennyweight  (=  24  grains) 

...  i ounce  (=  480  „ ) 

I pound  (=5760  „ ) 


Old  Apothecaries’  Weight  (superseded  in  1864). 

.20  Grains  ...  ...  ...  ...  1 scruple  (=  20  grains) 

3 Scruples  ...  ...  ...  ...  1 drachm  (=  60  „ ) 

8 Drachms ...  1 ounce  (=  480  „ ) 

12  Ounces  ...  ...  ...  ...  1 pound  (=  57^0  „ ) 

The  New  Apothecaries’  Weight  is  the  same  as  Avoirdupois. 


Liquid  Measure. 


-60  Minims 
8 Drachms  ... 
20  Ounces 
8 Pints 


i drachm 

I ounce  = 1*73  cub.  ins.  nearly 

I pint  = 34-66  „ „ 

I gallon  = 277-25  „ „ 


The  Imp.  Gallon  is  exactly  10  lbs.  Avoir,  of  pure  water ; the  pint,  lb. 


Fluid  Measure. 

I Minim  = i drop  I 2 Drs.  = i dessert  spoonful 

I Drachm  = l teaspoonful  | 4 ,,  = i table  „ 

French  Measures. 

I Gramme  ...  15*432  grains 

Kilogramme  ...  1000  grammes  (=2*2  lbs.  Avoir,  nearly) 

I Litre 35‘2i6  ounces  (fluid) 

I Cubic  Centimetre  (c.c.)  ...  17  minims  nearly 

(50  Cubic  Centimetres i ounce  6 drachms  5 minims 

I Metre  39-37  inches 


INDEX 


Amidol  Developer,  77 
Ammonia  Developer,  75 

Bath,  Fixing,  76 

Calculation  of  Efficiency  of 
Shutter,  43 

Candles,  Visual  Value  of  Sun- 
light in,  57 

Density,  Estimation  of,  in  a 
Negative,  83 
Developer,  Amidol,  77 
„ Ammonia,  75 

„ Metol,  77 

Development,  67 

„ in  White  Light,  74 
Diaphragm,  Use  of,  in  a Lens,  4 
Dirty  Lenses,  8 
Drum,  Rotating,  33 

Efficiency  of  a Shutter,  How 
Judged,  14 

Estimation  of  Speed  of  a Shutter, 
Rough,  17 

Fixing  Bath,  76 
Flare  Spot,  8 


Flash-Light,  Magnesium,  89 
Flat  Field  and  Lens,  5 

Green  Light  for  Developing 
Orthochromatic  Plates,  73 

Hand- Camera,  Movement  in  the, 
12 

Image,  Sharpness  of,  19 
Instantaneous,  Definition  of,  3 
Intensification,  79 
Intensifier,  Silver  Cyanide,  81 
Iris  Diaphragm,  Advantage  of, 

51 

Lantern,  Paper,  71 
Lens,  Testing  a,  5 
„ Effect  of  Thickness  and 
Colour  of  Glass  in  a,  7 
Lenses,  Dirty,  8 
Leyden  Jar  Spark,  91 

Magnesium  Flash-Light,  89 
Movement  in  the  Hand- Camera, 
12 

Mental  Impressions  of  Speed,  2 
Metol  Developer,  77 

H 


11. 


INDEX. 


Opacity  Required,  Range  of,  68 

Opacities,  Scale  of,  85 

Ortliochromatic  Plates,  63 
Ditto,  Green  Light  for  Develop- 
73 

Over-Exposure,  61 

Plates  for  Instantaneous  Work, 

53 

Pneumatic  Release  to  Shutter, 

52 

Range  of  Opacity  Required,  68 

Scale  for  use  in  trying  Rapidities 
of  Plates,  55 
„ of  Opacities,  85 
„ of  Vibration  for  Musical 
Notes,  27 

Sharpness  of  Image,  19 

Shutter,  at  Back  of  Lens,  10 
„ Best  Position,  9 
„ Diagrams,  22 -24, 34,35 

„ Efficiency  of,  14,  43 

„ in  Front  of  Lens,  10 
„ next  the  Plate,  1 1 
„ Pneumatic  Release,  52 
„ Speed  of,  1 7 


Sector  to  Estimate  Speed  of 
Shutter,  18 

Silver  Cyanide  Intensifier,  81 
Spark,  Duration  of,  92 
„ Leyden  Jar,  91 
Speed,  Estimation  by  Revolving 
Plate,  28 

„ Estimation  by  Pinholes 
round  Diaphragm,  31 
„ Mental  Impressions  of,  2 
,,  of  Rotation,  25 
Sunlight,  Visual  Value  of,  in 
Candles,  57 
Syren,  27 

Testing  a Lens,  5 
Thickness  and  Colour  of  Glass 
in  a Lens,  Effect  of,  7 
Tuning-Fork  for  Calculating 
Speed  of  Rotation,  27 

Vibration  for  Musical  Notes, 
Scale  of,  27 
View,  Choice  of,  87 
View-Finder,  Use  of,  88 
Views  in  Weak  Light,  59 

Yellow  Glass,  65 


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Mill  & Mm&  Company 

of  New  York, 

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the  “ Photographic  Times  Annual,”  etc.,  etc. 

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TRADE  AGENTS, 

6o  and  62  Bast  nth  Street,  New  York. 


